What is the X in X-mas?
Old English prættig (West Saxon), pretti (Kentish), *prettig (Mercian) "cunning, skillful, artful, wily, astute," from prætt, *prett "a trick, wile, craft," from West Germanic *pratt- (cf. Old Norse prettr "a trick," prettugr "tricky;" Frisian pret, Middle Dutch perte, Dutch pret "trick, joke," Dutch prettig "sportive, funny," Flemish pertig "brisk, clever"), of unknown origin.
Connection between Old English and Middle English words is uncertain, but if they are the same, meaning had shifted by c.1400 to "manly, gallant," and later moved via "attractive, skillfully made," to "fine," to "beautiful in a slight way" (mid-15c.). Ironical use from 1530s. For sense evolution, compare nice, silly. Also used of bees (c.1400). "After the OE. period the word is unknown till the 15th c., when it becomes all at once frequent in various senses, none identical with the OE., though derivable from it" [OED].
Meaning "not a few, considerable" is from late 15c. With a sense of "moderately," qualifying adjectives and adverbs, since 1560s. Pretty please as an emphatic plea is attested from 1902. A pretty penny "lot of money" is first recorded 1768.
"a pretty person or thing," 1736, from pretty (adj.).
early 13c., verbal noun from sit (v.). Meaning "a meeting of a body" is from c.1400. Meaning "interval during which one sits" (for some purpose, especially to have one's portrait taken) is from 1706. Sitting-room first recorded 1771. Slang sitting duck "easy target" first recorded 1944; literal sense is from 1867 (it is considered not sporting to shoot at one).
In a favorable position: “Abby finally got that promotion, and now she's sitting pretty.”
Quite; more than a little: The weather's pretty rotten (1565+)Related Terms
the attitude generally assumed in Palestine by those who were engaged in any kind of work. "The carpenter saws, planes, and hews with his hand-adze, sitting on the ground or upon the plank he is planning. The washerwoman sits by the tub; and, in a word, no one stands when it is possible to sit. Shopkeepers always sit, and Levi sitting at the receipt of custom (Matt. 9:9) is the exact way to state the case.", Thomson, Land and Book.