1520s, "a mushroom," from Latin fungus "a mushroom, fungus;" used in English at first as a learned alternative to mushroom (funge was used in this sense late 14c.). The Latin word is believed to be cognate with (or derived from) Greek sphongos, the Attic form of spongos "sponge" (see sponge, n.). "Probably a loanword from a non-IE language, borrowed independently into Greek, Latin and Armenian in a form *sphong- ...." [de Vaan]