The practice of writing messages on bombs is as old as bombs itself - because people were writing messages on missiles in general long before bombs were first used (11th/12th century China). One of the most popular and easy to use missiles was the lead or clay bullet, propelled by a sling, precise and deadly, in fact, for a long time this was more popular than the bow, especially in the Bronze age. Being made of lead from the 5th century BC on, they were quite easy to manipulate, and so we find text written on them as far back as hellenistic times (4th/3rd century BC). I couldn't find any reference on markings on the clay bullets of the old mesopotamian cultures, though.
I couldn't find any reference to the use of inscriptions of sling bullets in the old mesopotamian cultures, but we find simple writing on them in the 4th and 3rd century. Mostly only the names of the unit, or the commander, like a simple 'A' or 'L XIII' for 13th legion; but you also had little messages suh as 'ΔΕΞΑΙ' or 'catch/take this' written on them, as in this example from 1st century BC Athens
In the 1st century, we find the texts getting a little more elaborate in general. The most famous example is from bullets recovered from the battlefield of Perusia (modern Perugia), where Lucius Antonius and his brother's (Marcus Antonius/Mark Antony) wife Fulvia were besieged by the troops of Octavian (later the famous emperor Augustus) in 40 BC. Funditores, or slingers, were an elite troop that the Roman army liked to use in sieges, both on the defense and the offense. They were well suited to attacking defenders on the walls with precise and deadly missiles. These bullets contain a lot of NSFW inscriptions.
Here's a drawing of some of them
Translated, they say the following:
- Simply the name of the Commander (Scaeva) of a unit of the XIIth legion
- 12th 'victorious' Legion
- I search Fulvia's clit
- You are hungering, and you try to hide it from me (i.e. we know you guys are starving in/out there)
- A bullet of the XIth legion with a dedication to the deified Julius Caesar
- Relax your seat (ass), Octavian (in today's internet parlance, 'prepare your anus')
7.-10. are names of commanders again
-11. Just a picture of a dick.
There are more with such lovely messages as "I search Octavians ass", "Bald Lucius Antonius and Fulvia, prepare your asses", "Greetings, Octavian, cocksucker", or simply "take this, Octavian".
The penetrating nature of these missiles is here delightfully coupled with a not-so-subtle assault on the sexual preferences of Lucius and Octavian - being the receptive part was considered aberrant and not acceptable for an adult male. Consider also that the name for such a missile in the singular is glans.
I can't say much about the practice in the middle ages and the early modern age, but I suspect that you will find this practice in most places where people use missiles that can be written on or incised in some way to mark them.
