today i founds out that the english word 'elf' and the german word 'alb' are cognate; also, that 'alb' is the modern germanic spelling of 'alp'. so that got me wondering if there was some connection to mountain range of the same name that divides parts of northern europe from the mediterranean region. when looking into that, all i could find was that 'alps' is the latin name for the mountain range, so that proved to be a bit of a dead-end. however, since latin and german are both members of the indo-european language family, perhaps there was some older connection.
perhaps this would be a question better suited to linguists or something, but i'd think that there is such a thing as a 'language historian' and i think general historians might know of any folklore from ancient indo-european cultures of creatures coming from (or escaping to) mountainous areas to infiltrate people's dreams or otherwise disturb them during sleep (albtraum is the german equivalent to nightmare, literally translates to 'elf dream').
thanks in advance for any prospective answers!
The use of words, in various places in Europe, associated with the word 'elf' does not represent an allusion to the mountains - if that is what you're asking. The term as applied to the river Elbe, the Alps, and to the supernatural beings apparently all draw on the idea that these things are bright and/or shimmer in some way.
Referring to the supernatural beings as the 'bright or shimmering ones' is reminiscent of referring to them as the 'good neighbors', 'the good folk', the 'wee folk', the hidden ones, or any number of terms. This observation would seem to imply that 'elf' is a circumlocution, that is that there was a proper name for the supernatural beings that was being being avoided because it might be regarded as discourteous to utter. These sorts of circumlocutions are common in various languages: some Native American avoid naming mountains within sight of the mountain because it would be disrespectful; bears in the northern latitudes are often referred to as something other than their proper name, and sometimes the circumlocution causes the extinction of the original term because it was 'circumlocuted' out of existence. The English term 'bear' refers to the brown color of the animal - that is, it is the 'brown one', which was a more polite way to refer to the animal than with its proper name which was related to the Latin term 'ursus' but is extinct in English. Similarly, the bear is often referred to in other languages by names that refer to its attraction to honey.
In the case of 'elf', however, it does not seem that there was an original term that was avoided and became extinct. Instead, these sorts of supernatural beings were always referred to in descriptive ways. Nevertheless, it does seem that as language evolved and people forgot the original meaning of the descriptive term, that these words could assume the role of a proper name, which then needed to be avoided. Thus, 'elf' became a term that many people came to regard as too direct and discourteous, and so they employed some of the other descriptive terms if they felt they elves might overhear the conversation.