Yours, Etc.: Origins and Uses of 8 Sign-Offs
late 14c., "rejoice, be glad" (intransitive), from Old French enjoir "to give joy, rejoice, take delight in," from en- "make" (see en- (1)) + joir "enjoy," from Latin gaudere "rejoice" (see joy); Sense of "have the use or benefit of" first recorded early 15c. (replacing Old English brucan; see brook (v.)).
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. Related: Enjoyed; enjoying; enjoys.
An exhortation to be happy, to enjoy oneself: Go. Read. Enjoy. It couldn't hurt/ The trooper grinned. ''Enjoy,'' he said, and walked on toward the cruiser
[1980s+; fr a Yiddish speech pattern, recorded but not approved by Leo Rosten]