There were bosses in games ever since 1975, and I don’t think I really have to define ‘boss’ here. But how did the word get stuck? And when was the first time when the challenging enemy was referred to as a ‘boss’?
Sorry for the necro. I find this immensely interesting, and have done some deep digging and made a video about the topic:
The earliest source I found is from a 1980 arcade operating manual of Space Panic, mentioning bosses. Another enemy in that game is a ‘don’.
In early 1980’s Japan, “bosu” (loanword from English) had a derogatory connotation to do with Mafia. Translating “bosu” would give you “boss”, but in English the negative meaning is not present.
Old Kung Fu films use this term for mobsters too (Bruce Lee in The Big Boss).