1850, "pertaining to a groove," from groove (n.) + -y (2). Slang sense of "first-rate, excellent" is 1937, American English, from jazz slang phrase in the groove (1932) "performing well (without grandstanding)." As teen slang for "wonderful," it dates from c. 1941; popularized 1960s, out of currency by 1980. Earlier colloquial figurative sense was "having a tendency to routine, inclined to a specialized and narrow way of life or thought" (1882). Related: Grooviness.