Upvote:4
I do not know if this is the earliest, but the first mention of Kish is from tablets from the Jemdet Nasr period dating somewhere between 3100β2900 BCE.
The first Sumerian reference is from the list of kings:
"After the flood had swept over, and the kingship had descended from heaven, the kingship was in Kish."
Though i am not sure if some ancient cities were "officially" named by someone. I wouldn't be surprised if ancient cities were named like how most towns got there name in the middle ages in Europe. By locals referring to it by where it is, or what it makes.