spunk (n.)

Old English sponge, spunge, "absorbent and porous part of certain aquatic organisms," from Latin spongia "a sponge," also "sea animal from which a sponge comes," from Greek spongia, which is related to spongos "sponge," which is of unknown origin; Beekes calls it "an old Wandewort." "Probably a loanword from a non-IE language, borrowed independently into Greek, Latin and Armenian in a form *sphong-" [de Vaan]. The Latin word is the source of Old Saxon spunsia, Middle Dutch spongie, Old French esponge, Spanish esponja, Italian spugna.

In English the word is used in reference to the marine animal from 1530s; of any sponge-like substance from c. 1600. Figurative use in reference to one who absorbs without discrimination is by c. 1600. The meaning "one who persistently and parasitically lives on others" is by 1838 (compare the verb, and see sponger).

To throw in the sponge "quit, submit" (1860) is from prizefighting, in reference to the sponges used to cleanse the faces of combatants between rounds (compare later throw in the towel). Sponge-cake, light and sweet, is attested by 1801, so called for its substance.

"inferior, bad," 1896, also as a noun, "something worthless," earlier "rotten wood used as tinder" (1680s), "A word in common use in New England, as well as in the other Northern States and Canada" [Bartlett]; perhaps from Delaware (Algonquian) ponk, literally "dust, powder, ashes;" but Gaelic spong "tinder" also has been suggested (compare spunk "touchwood, tinder," 1580s).

"courageous, spirited, unwilling to give up, full of spunk," 1786, from spunk (n.) + -y (2). The Scottish sense of "showing a small fire or spark" is attested from 1791. Related: Spunkily; spunkiness.