I’m not sure if “kudos to…” is a phrase per se. Gail?
Do you mean to ask where the word “kudos” came from?
In which case, I agree with Gail. Word came before the candy bar.
gailcalled: I guess we’re looking in different OEDs, because my OED says the word is from Greek kudos “praise, renown” and is singular. There was no singular kudo, plural kudos – kudos was singular in Greek. In English it seems to have been turned into a plural noun, since it ends in “s”.