An Etymological Dictionary of Astronomy and Astrophysics

(adverb & preposition) From a place or position; at a distance in space or time. So as to be separated from support.

See also: M.E., from O.E. of “away, away from;” cf. Du. af “off, down,” Ger. ab “off, from, down;” PIE *apo- “off, away,” → apo-.