c. 1300, "off to one side;" mid-14c., "to or from the side;" late 14c., "away or apart from a normal direction or position, out of the way," from a- (1) "on" + side (n.). Noun sense of "words spoken so as to be (supposed) inaudible" is from 1727. Middle English had asidely "on the side, indirectly" (early 15c.) and asideward "sideways, horizontal" (late 14c.). Used colloquially as a preposition from 1590s.
Entries linking to aside
prefix or inseparable particle, a relic of various Germanic and Latin elements.
In words derived from Old English, it commonly represents Old English an "on, in, into" (see on (prep.)), as in alive, above, asleep, aback, abroad, afoot, ashore, ahead, abed, aside, obsolete arank "in rank and file," etc., forming adjectives and adverbs from nouns, with the notion "in, at; engaged in." In this use it is identical to a (2).
It also can represent Middle English of (prep.) "off, from," as in anew, afresh, akin, abreast. Or it can be a reduced form of the Old English past participle prefix ge-, as in aware.
Or it can be the Old English intensive a-, originally ar- (cognate with German er- and probably implying originally "motion away from"), as in abide, arise, awake, ashamed, marking a verb as momentary, a single event. Such words sometimes were refashioned in early modern English as though the prefix were Latin (accursed, allay, affright are examples).
In words from Romanic languages, often it represents reduced forms of Latin ad "to, toward; for" (see ad-), or ab "from, away, off" (see ab-); both of which by about 7c. had been reduced to a in the ancestor of Old French. In a few cases it represents Latin ex.
[I]t naturally happened that all these a- prefixes were at length confusedly lumped together in idea, and the resultant a- looked upon as vaguely intensive, rhetorical, euphonic, or even archaic, and wholly otiose. [OED]
Old English side "flanks of a person, the long part or aspect of anything," from Proto-Germanic *sīdō (source also of Old Saxon sida, Old Norse siða, Danish side, Swedish sida, Middle Dutch side, Dutch zidje, Old High German sita, German Seite), from adjective *sithas "long" (source of Old English sid "long, broad, spacious," Old Norse siðr "long, hanging down"), from PIE root *se- "long, late" (see soiree).
Original sense preserved in countryside. Figurative sense of "position or attitude of a person or set of persons in relation to another" (as in choosing sides) first recorded mid-13c. Meaning "one of the parties in a transaction" is from late 14c.; sense in a sporting contest or game is from 1690s. Meaning "music on one side of a phonograph record" is first attested 1936. Phrase side by side "close together and abreast" is recorded from c. 1200. Side-splitting "affecting with compulsive laughter" is attested by 1825.
put her sewing aside when he entered
threw the book aside
stood aside to let him pass
brush the objections aside
all joking aside, I think you're crazy
a day set aside for relaxing