c.1200, from Old English on life "in living." The fuller form on live was still current 17c. Alive and kicking "alert, vigorous," attested from 1859; "The allusion is to a child in the womb after quickening" [Farmer]. Used emphatically, especially with man; e.g.:
[A]bout a thousand gentlemen having bought his almanacks for this year, merely to find what he said against me, at every line they read they would lift up their eyes, and cry out betwixt rage and laughter, "they were sure no man alive ever writ such damned stuff as this." [Jonathan Swift, Bickerstaff's Vindication, 1709]Thus abstracted as an expletive, man alive! (1845).
Get ready; act alert; get ready to move: Look alive, the train's coming