Origin and history of alee

Middle English le, leoh, from Old English hleo "shelter, cover, defense, protection," from Proto-Germanic *khlewaz (source also of Old Norse hle, Danish læ, Old Saxon hleo, Dutch lij "lee, shelter"). The original sense is uncertain; it might have been "warm" (compare German lau "tepid," Old Norse hly "shelter, warmth"), and Watkins traces it to a PIE *kle-wo-, a suffixed variant form of the root *kele- (1) "warm."

Nautical sense "that part of the hemisphere to which the wind is directed" (c. 1400) is of Scandinavian origin, from the notion of the side of the ship opposite that which receives the wind as the sheltered side. As an adjective, 1510s, from the noun. The lee shore is that toward which the wind blows. Middle English also had lewth "warmth, shelter," Old English hleowþ, with Proto-Germanic abstract noun suffix *-itho (see -th (2)). Also compare lukewarm.

prefix or inseparable particle, a conglomerate 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," athree (adv.) "into three parts," etc. In this use it forms adjectives and adverbs from nouns, with the notion "in, at; engaged in," and 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).

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, 1989]