landlady n.

Old English lond, land, "ground, soil," also "definite portion of the earth's surface, home region of a person or a people, territory marked by political boundaries," from Proto-Germanic *landja- (source also of Old Norse, Old Frisian Dutch, Gothic land, German Land), perhaps from PIE *lendh- (2) "land, open land, heath" (source also of Old Irish land, Middle Welsh llan "an open space," Welsh llan "enclosure, church," Breton lann "heath," source of French lande; Old Church Slavonic ledina "waste land, heath," Czech lada "fallow land"). But Boutkan finds no IE etymology and suspects a substratum word in Germanic,

Etymological evidence and Gothic use indicates the original Germanic sense was "a definite portion of the earth's surface owned by an individual or home of a nation." The meaning was early extended to "solid surface of the earth," a sense which once had belonged to the ancestor of Modern English earth (n.). Original senses of land in English now tend to go with country. To take the lay of the land is a nautical expression. In the American English exclamation land's sakes (1846) land is a euphemism for Lord.

c. 1200, lafdi, lavede, from Old English hlæfdige (Northumbrian hlafdia, Mercian hlafdie), "mistress of a household, wife of a lord," apparently literally "one who kneads bread," from hlaf "bread" (see loaf (n.)) + -dige "maid," which is related to dæge "maker of dough" (which is the first element in dairy; see dey (n.1)). Also compare lord (n.)). Century Dictionary finds this etymology "improbable," and OED rates it "not very plausible with regard to sense," but no one seems to have a better explanation.

The medial -f- disappeared 14c. The word is not found outside English except where borrowed from it. Sense of "woman of superior position in society" is c. 1200; that of "woman whose manners and sensibilities befit her for high rank in society" is from 1861 (ladylike suggesting this sense is attested from 1580s, and ladily from c. 1400). Meaning "woman chosen as an object of chivalrous love" is from early 14c. Used commonly as an address to any woman since 1890s.

Applied since Old English to the Holy Virgin, hence many extended usages in plant names, place names, etc., from genitive singular hlæfdigan, which in Middle English merged with the nominative, so that lady- often represents (Our) Lady's, as in ladybug. Lady Day (late 13c.) was the festival of the Annunciation of the Virgin Mary (March 25). Ladies' man first recorded 1784; lady-killer "man supposed to be dangerously fascinating to women" is from 1811. Lady of pleasure recorded from 1640s. Lady's slipper as a type of orchid is from 1590s.