Is it ensure, insure, or assure?
1670s, "a severe blow," probably from a Scandinavian source (cf. Norwegian slamre, Swedish slemma "to slam, bang") of imitative origin. Meaning "a violent closing of a door" is from 1817. Meaning "an insult, put-down" is from 1884. Slam-bang recorded by 1806 (also slap-bang, 1785). Slam-dunk is from 1976; early use often in reference to Julius Erving. Slam-dance is attested by 1987 (slam by itself in this sense is recorded from 1983).
"a winning of all tricks in a card game," 1660s, earlier the name of a card game (also called ruff), 1620s, used especially in whist, of obscure origin. Grand slam in bridge first recorded 1892; earlier in related card games from 1814; figurative sense of "complete success" is attested from 1920; in baseball sense from 1935.
1690s, "to beat, slap;" 1775 as "to shut with force," from slam (n.1). Meaning "throw or push with force" is from 1870. Meaning "say uncomplimentary things about" is from 1916. Related: Slammed; slamming.
Someone who is an expert at slacking off: don't want to be called a slackmaster