lo (interj.) Look up lo at Dictionary.com
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"].