"to move heavily or unsteadily," 1520s, probably from Old Norse sveggja "to swing, sway," cognate with Old English swingan "to swing" (see swing). Related: Swagged; swagging.
"ornamental festoon," 1794, from swag (v.). Colloquial sense of "promotional material" (from recording companies, etc.) was in use by 2001; swag was English criminal's slang for "quantity of stolen property, loot" from c.1839. Earlier senses of "bulky bag" (c.1300) and "big, blustering fellow" (1580s) may represent separate borrowings from the Scandinavian source. Swag lamp attested from 1966.