fruitless (adj.)

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 1927. 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.

word-forming element meaning "lacking, cannot be, does not," from Old English -leas, from leas "free (from), devoid (of), false, feigned," from Proto-Germanic *lausaz (cognates: Dutch -loos, German -los "-less," Old Norse lauss "loose, free, vacant, dissolute," Middle Dutch los, German los "loose, free," Gothic laus "empty, vain"), from PIE root *leu- "to loosen, divide, cut apart." Related to loose and lease.

*bhrūg-, Proto-Indo-European root meaning "to enjoy," with derivatives referring to agricultural products.

It forms all or part of: brook (v.) "to endure;" defunct; fructify; fructose; frugal; fruit; fruitcake; fruitful; fruition; fruitless; frumentaceous; function; fungible; perfunctory; tutti-frutti; usufruct.

It is the hypothetical source of/evidence for its existence is provided by: Latin frui "to use, enjoy," fructus "an enjoyment, proceeds, fruit, crops;" Old English brucan "use, enjoy, possess," German brauchen "to use."