You should probably get what word I’m doing. If not, you may need to see a specialist.
There’s no date for when kiss showed up, but it is known that it was cuss in Middle English (no relation), and before that, coss (as a noun) and cyssan (as a verb) in Old English. Cyssan can be traced to the Proto Germanic kussijanan, and it’s thought that the kuss- part of the word is supposed to be onomatopoeia of the sound it makes.
Now try not to think about that the next time you kiss someone.
University of Texas at Austin Linguistic Research Center
Tony Jebson’s page on the Origins of Old English