away: [OE] Away was formed in the late Old English period by conflating the phrase on weg, literally ‘on way’, that is, ‘on one’s way, departing’. This soon became reduced to aweg, hence away. => way
late Old English aweg, earlier on weg "on from this (that) place;" see a- (1) + way (n.). Colloquial use for "without delay" (fire away, also right away) is from earlier sense of "onward in time" (16c.). Intensive use (as in away back) is American English, first attested 1818.
