Lo
natural exclamation: first recorded as lā in Old English; reinforced in Middle English by a shortened form of loke ‘look!’, imperative of look.
wiktionary
From Middle English lo, loo, from Old English lā(“exclamation of surprise, grief, or joy”). Conflated in Middle English with lo!(interjection), a corruption of lok!, loke!(“look!”) (as in lo we!(look we!)). Cognate with Scots lo, lu(“lo”). See also look.
Variant of low.
lo
etymonline
lo (interj.)
early 13c., from Old English la, exclamation of surprise, grief, joy, or mere greeting; probably merged with or influenced in Middle English by lo!, which is perhaps short for lok "look!" imperative of loken "to look" (see look (v.)). Expression lo and behold attested by 1779. In old U.S. slang, Lo was a generic name for an Indian or the Indians collectively (1871), jocularly from Pope's line "Lo, the poor Indian" ["Essay on Man"].
