1670s, "a bottom, the bottom; foundation, groundwork," from French fond "a bottom, floor, ground" (12c.), also "a merchant's basic stock or capital," from Latin fundus "bottom, foundation, piece of land" (from PIE root *bhudh- "bottom, base," source also of Sanskrit budhnah, Greek pythmen "foundation, bottom," Old English botm "lowest part;" see bottom (n.)). Meaning "stock of money or wealth available for some purpose" is from 1690s; sense of "store of anything to be drawn upon" is from 1704. Funds "money at one's disposal" is from 1728.
mid-15c., "primary, original, pertaining to a foundation," modeled on Late Latin fundamentalis "of the foundation," from Latin fundamentum "foundation" (see fundament). In music (1732) it refers to the lowest note of a chord. Fundamentals (n.) "primary principles or rules" of anything is from 1630s.
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]
"capable of being used in place of another; capable of being replaced," 1818, a word in law originally, from Medieval Latin fungibilis, from Latin fungi "perform" (see function (n.)) via phrases such as fungi vice "to take the place." Earlier as a noun (1765).
1776, "convert (a debt) into capital or stock represented by interest-bearing bonds," from fund (n.). Meaning "supply (someone or something) with money, to finance" is from 1900.
1844, "perform a function" (intransitive), from function (n.). Related: Functioned; functioning.