smack n.1

"a taste, flavor, savor" especially a slight flavor that suggests something, Middle English smakke, from Old English smæc "taste; scent, odor," from Proto-Germanic *smakka- (source also of Old Frisian smek, Middle Dutch smæck, Dutch smaak, Old High German smac, German Geschmack, Swedish smak, Danish smag), from verb *smakjanan, from a Germanic and Baltic root meaning "to taste" (source also of Lithuanian smaguriai "dainties," smagus "pleasing").

The transferred meaning "a trace (of something)" is attested from 1530s.

"part the lips so as to make a sharp sound," as if in relish or anticipation, 1550s, probably of imitative origin (compare smack (v.2)). The sense of "kiss," especially in a noisy manner, is by 1870.

1560s, "smart, sharp sound made by the lips," as in kissing or tasting, from smack (v.1). The meaning "a loud kiss" is recorded from c. 1600. That of "slap, sharp sudden blow with the flat of the hand" is by 1746.

single-masted sailboat, formerly much used in the coasting and fishing trade, 1610s, probably from Dutch or Low German smak "sailboat," perhaps from smakken "to fling, dash" (see smack (v.2)), and perhaps so-called from the sound made by its sails. French semaque, Spanish zumaca, Italian semacca probably are borrowings from Germanic languages.

"heroin," 1942, American English slang, probably an alteration of schmeck "a drug," especially heroin (1932), from Yiddish schmeck "a sniff," from Germanic (see smack (n.1)).

1801, "hit so as to produce a sharp sound;" especially "sharply strike a flat surface with the inside of the hand," 1835, from smack (n.2) in the sense of "sharp sound made by hitting" (1746); perhaps influenced by Low German smacken "to strike, throw," in any case likely ultimately of imitative origin. Compare Swedish smak "slap," Middle Low German smacken, Frisian smakke, Dutch smakken "to fling down," Lithuanian smogti "to strike, knock down, whip."

The general sense of "strike (anything) with great force" is by 1882 in sports.

mid-13c., smacchen, "to smell (something"); mid-14c., "to taste (something), perceive by sense of taste" (transitive); late 14c. "to have a taste, taste of" (intransitive), from smack (n.1). Or perhaps from Old English smæccan (Mercian) "to taste." Compare Old Frisian smakia Middle Dutch smaecken, Old High German smakken "have a savor, scent, or taste," German schmecken "taste, try, smell, perceive." Sometimes also smatch.

Now mainly in verbal figurative use smacks of ... "has a certain character or property," attested by 1590s, in the literal sense "give off an odor" it is attested is by c. 1300: "Commonly but erroneously regarded as identical with [smack (n.2)], as if 'taste' proceeds from 'smacking the lips.'" [Century Dictionary]

"suddenly, directly, aggressively, plump, straight," 1782, from smack (v.1); the extended form smack-dab is attested from 1892, American English colloquial (slap-dab is from 1886).