Although the transitions were gradual, and exact dates for the demarcation of the Middle Ages are misleading, convention often places the beginning of the period between the death of the Roman emperor Theodosius I in 395 and the fall of Rome to the Visigoths in 410. The Dark Ages, formerly...
1850, "pertaining to a groove," fromgroove(n.) +-y(2). The slang sense of "first-rate, excellent" is by 1937, American English, from jazz slang phrasein the groove(1932) "performing well" (without grandstanding). As teen slang for "wonderful," it dates from c. 1941; popularized mi...