fruitcake (n.)

late 12c., "any vegetable product useful to humans or animals," from Old French fruit "fruit, fruit eaten as dessert; harvest; virtuous action" (12c.), from Latin fructus "an enjoyment, delight, satisfaction; proceeds, produce, fruit, crops," from frug-, stem of frui "to use, enjoy," from suffixed form of PIE root *bhrug- "to enjoy," with derivatives referring to agricultural products. The Latin word also is the source of Spanish fruto, Italian frutto, German Frucht, Swedish frukt-.

Originally in English meaning all products of the soil (vegetables, nuts, grain, acorns); modern narrower sense is from early 13c. Also "income from agricultural produce, revenue or profits from the soil" (mid-14c.), hence, "profit," the classical sense preserved in fruits of (one's) labor.

Meaning "offspring, progeny, child" is from mid-13c.; that of "any consequence, outcome, or result" is from late 14c. Meaning "odd person, eccentric" is from 1910; that of "male homosexual" is from 1935, underworld slang. The term also is noted in 1931 as tramp slang for "a girl or woman willing to oblige," probably from the fact of being "easy picking." Fruit salad is attested from 1861; fruit-cocktail from 1900; fruit-bat by 1869.

early 13c., "flat or comparatively thin mass of baked dough," from Old Norse kaka "cake," from West Germanic *kokon- (source also of Middle Dutch koke, Dutch koek "a cake, gingerbread, dumpling," Old High German kuohho, German Kuchen "a cake, a tart"). Not believed to be related to Latin coquere "to cook," as formerly supposed. Replaced its Old English cognate, coecel.

What man, I trow ye raue, Wolde ye bothe eate your cake and haue your cake? ["The Proverbs & Epigrams of John Heywood," 1562]

Extended mid-15c. to any flat, rounded mass. From early 15c. extended to "a light composition of flour, sugar, butter and other ingredients baked in any form." To take the cake "win all, rank first" (often ironic) is from 1847, American English; piece of cake "something easy" is from 1936. The let them eat cake story is found in Rousseau's "Confessions," in reference to an incident c. 1740, long before Marie Antoinette, though it has been associated with her since c. 1870; it apparently was a chestnut in the French royal family that had been told of other princesses and queens before her.