"greetings!" c.1200, from a Scandinavian source, cf. Old Norse heill "health, prosperity, good luck;" and from Old English hals, shortening of wæs hæil "be healthy" (see health and cf. wassail).
"frozen rain," Old English hægl, hagol (Mercian hegel) "hail, hailstorm," also the name of the rune for H, from West Germanic *haglaz (cf. Old Frisian heil, Old Saxon, Old High German hagal, Old Norse hagl, German Hagel "hail"), probably from PIE *kaghlo- "pebble" (cf. Greek kakhlex "round pebble").
"to call from a distance," 1560s, originally nautical, from hail (interj.). Related: Hailed; hailing. Hail fellow well met is 1580s, from a familiar greeting. Hail Mary (c.1300) is the angelic salutation (Latin ave Maria), cf. Luke i:58, used as a devotional recitation. As a desperation play in U.S. football, attested by 1940. To hail from is 1841, originally nautical. "Hail, Columbia," the popular patriotic song, was a euphemism for "hell" in American English slang from c.1850-1910.