"to endure," Old English brucan "to use, enjoy the use of, possess; eat; cohabit with," from Proto-Germanic *brukjanan "to make use of, enjoy" (source also of Old Saxon brukan, Old Frisian bruka "to use, practice," Dutch gebruiken "to use," Old High German bruhhan, German brauchen "to use, need," Gothic brukjan), from PIE root *bhrug- "to enjoy." Sense of "use" as applied to food led to "be able to digest," and by 16c. to "endure, tolerate," always in a negative sense. The original meanings have become obsolete.
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."
Transitive meaning "take pleasure in" is mid-15c. In modern use it has a tendency to lose its connection with pleasure: newspaper photo captions say someone enjoys an ice cream cone, etc., when all she is doing is eating it, and Wright's "English Dialect Dictionary" (1900) reports widespread use in north and west England of the phrase to enjoy bad health for one who has ailments. Meaning "have sexual relations with" (a woman) is from 1590s. Related: Enjoyed; enjoys; enjoying. To enjoy oneself "feel pleasure or satisfaction in one's mind" attested by 1708.