Anglo Saxon noble titles are interesting in two senses: they change pretty radically over the course of the anglo-saxon period (c.500-1066), and even when looking at contemporary sources that agree in date, they may not agree in title-usage.

First off, there are a couple issues with what you've written. King Cnut may not have been the best choice of example, because he is not Anglo-Saxon, he was a Dane. The Danish method of patronymic surname (x-son) was not prevalent, at least in that form, in Anglo-Saxon society. Secondly, the titles such as Alfred "the Great," Æthelred "the Unready," or Cnut "the Great," were posthumous additions. Glaringly in the case of Æthelred, the title "Unready" is not ascribed to him for centuries, and is a late medieval insertion.

Those things considered, to delve into Anglo-Saxon noble titles is to delve into the chronology of the era. The idea of lordship and nobility meant widely different things from the early to late Anglo-Saxon period. Some of the earliest references to nobles (besides kings) calls them eorls, which seems to be a catch-all for any sort of noble. This appears exclusively in Kent, and disappears fairly quickly. What replaces the eorl in terminology is the gesith. Gesith is an interesting title. Directly translated, it means something along the lines of honourable comrade (assumably to the king). Likewise, in Beowulf the warband of Beowulf are referred to as gesiths in the plural. The idea here seems rooted in the idea of military retinue, which was a constant feature of kingship in the seventh and eighth centuries, and was preserved in various forms well beyond that.

What was it to be a gesith though? Could anyone with brute strength join the king's retinue? It seems, to me at least, that gesith-status was conveyed onto people already of considerable landed wealth. There are several discrepancies in early law codes that point towards this, and to look at those a distinction on land needs to be made. For Anglo-Saxons, there were two working definitions of land. Firstly, land that you owned, ploughed, and payed tribute for. Secondly, was land that you received tribute from. A practice in early Anglo-Saxon society was for a gesith, after spending enough time in the king's retinue, was granted land to settle down and marry. This land was transferred from the king, who was giving the right to collect tribute to the gesith in question (in this case then, the second form of land). However, the laws of Ine refer to gesith-cund who already have land, but are not performing military service. If military service in a retinue was needed to attain land from the king, these gesiths must already have land in the form of the first type: land they directly owned, and from which paid tribute to the king, or possibly to another noble. It stands to reason, then, that a gesith was a freeman who had acquired land over time (perhaps generations), and possessed enough land to then serve with the king.

As time went on, though, the term gesith fell out of popularity, and by the late eighth century the word thegn was in dominant use. Once again, the root of the word is interesting, as it translates literally to servant or servile person. In its earliest instances, thegn seems to have meant just that. An early Old English translation of Gregory's Dialogues translates a servant at a feast to thegn, a far cry from the noble title it would come to convey. It seems that thegns may have been initially unlanded men, who through service to the king were able to gain land (i.e. tribute rights). As time went on, important distinction is made when referring to thegns between a king's thegn and a lesser thegn, something that actually features prominently in Cnut's law code. Possibly, any noble of enough import could have a thegn.

What this shift from gesith to thegn in language straddles is the concurrent shift from moveable wealth to landed wealth in Anglo-Saxon society, and later changes in concepts of landed wealth, which are vital to understanding nobility. No mention is made of the gesiths of Beowulf owning land or ever receiving land. Instead, value is placed on great gifts, in the form of rings, gold, swords, horses, and other valuable possessions. This moveable wealth is the mark of a noble, irregardless of landed possessions. As time goes on, though, this becomes explicitly untrue. A set of status regulations from the Textus Roffensis (from the early eleventh century) state that if a ceorl (a free farmer) "prospered, that he possessed fully five hides of land of his own, a bell and a castle-gate, a seat and special office in the king's hall, then he was henceforth entitled to the rights of a thegn." Other texts are even more straightforward, saying that ownership of a sword and shield no longer sufficed for thegn-ship, instead five hides was necessary. With this shift from personal accoutrements to landed titles, also came a shift in what it meant to own land. Early translations of landlord in Anglo-Saxon documents describes them as "loaf-guardians" or "beer-guardians," while tenants and inhabitants of that land are "loaf-givers." Accordingly, the tribute tied to the land was accounted for in food-rent, and revolved in legal terms around how much food would be needed to support the king's court for one night, or an annual render. This is seen too in concepts of inland and warland. Essentially, a grant of land from a King would contain a portion of inland, which the recipient could plough and own directly, and another portion of warland, from which the recipient exacted tribute. This idea, called superiority or extensive lordship, eventually gave way to intensive lordship. As seen in the status regulation mentioned above, by the eleventh century land alone no longer sufficed, thegnly status needed certain buildings as well. These imply a developing reciprocity in landlord-tenant relationships. A bell was needed (and by extension a church) to provide pastoral care and christian communion. A castle-gate to offer protection under attack. These aspects are the formation of the idea of the English manor, of a landed noble with a distinct, small, territory, ruled from a fortified location. Earlier ideas of land were much more fluid, rooted in the mobility of nobles. The laws of Ine (late seventh century) stipulate that a gesith can move house, but in doing so can only bring his reeve, smith, and family. Later laws make no such consideration. Likewise, as time went on the king's court, which had originally travelled throughout southern England, increasingly settled in a few locations (namely London and Winchester).

These then, are the core of nobility for Anglo-Saxons. Whether gesith or thegn, the essence ultimately boiled down to a landed noble, of enough wealth to merit status. Between these and the king lay ealdormen. These were not heritable titles, but were instead appointed by the king. Furthermore, ealdormanries were not fixed in the later Anglo-Saxon period, but rather their territories could fluctuate from one king to the next. These ealdormen seem to have evolved from earlier hegemonies, and the concept of sub or client kings. Essentially, ealdormen acted as a more local representative of the king, and in that authority acted in many cases independent of the king. In the Anglo-Saxon Chronicle, for example, most descriptions of battles say that an ealdorman went out to fight, and in these cases makes no mention of kings' involvement in the actual fighting nor in giving the order to fight. The power of ealdormen was immense, and in some instances rivalling the king. During the final years of Æthelred II's reign, Eadric Streona (the ealdorman of Mercia), actively rebelled and joined sides with Swein Forkbeard and later Cnut. Despite this, Æthelred seems unable to revoke Eadric's title, or really do anything to combat such blatant treason. Likewise, Godwine's rebellion of 1051 left King Edward hapless were it not for the intervention of the other major ealdormen of the realm, Sigeberht and Leofwine. The idea of what these ealdormen were seems less sharply delineated than that of a thegn. Contemporary Latin translations would refer to an ealdorman variously as dux, primates, satrapes, or proceres. These all connote slightly different meanings, and really the only firm thing that can be settled on is that ealdormen were extremely powerful.

Considering all this, Anglo-Saxon noble titles can be stratified into two tiers beneath the king: a landholding class of minor nobles, and the major power figures answerable (sometimes just nominally) only to the king. Throughout the half-millenia that these concepts dominated Britain, what it meant to be noble changed, seen in the evolution of titles from eorl to gesith to thegn. That said, even what I've offered above is a gross oversimplification, and does not consider the massive difference in royal authority and therefore expressions of nobility north and south of the Humber, nor adequate consideration of the numerous kingdoms present in England for much of its history. The broad brushstrokes I've outlined, though, do recur throughout the Anglo-Saxon period, and can be taken at large for concepts of noble titles in Anglo-Saxon Britain in their respective timeframes. I haven't touched on your examples of Cnut because, frankly, they had nothing to do with noble titles. Surnames, if one had them, could just as easily be a nickname as a patronym (such as the ealdorman Wulfric Spott, alternatively called Wulfric son of Wulfrune). While they may have brought prestige or connoted lineage to these people, noble titles were rooted in the more standardised notions of thegn and ealdorman.

Sources:

Beowulf, transl. Seamus Heaney

Unification and Conquest by Pauline Stafford

English Historical Documents ed. Dorothy Whitelock no.'s 1, 32, 49, 51

"Gesiths and Thegns in Anglo-Saxon England from the Seventh to the Tenth Century" H. R. Loyn