1570s, "that hums," present-participle adjective from hum (v.). Meaning "brisk, vigorous, energetic" is from 1680s. Related: Hummingly. Humming-bird (1630s) so called from sound made by the rapid vibration of its wings.
There is a curious bird to see to, called a humming bird, no bigger then a great Beetle. [Thomas Morton, "New English Canaan," 1637]