as a closing in letters, "respects, good wishes," by 1775, from regard (n.) in the sense of "esteem, affection" (late 14c.).
Entries linking to regards
regard n.
mid-14c., "a consideration; a judgment," from Old French regard, regart, from regarder "take notice of," from re-, here perhaps an intensive prefix, + garder "look, heed," from a Germanic language (see guard (n.)).
Meanings "a look, appearance; respect, esteem, favor, kindly feeling which springs from a consideration of estimable qualities" all are recorded late 14c. Phrase in regard to is from mid-15c. (Chaucer uses at regard of).