"a taste, flavor, savor" especially a slight flavor that suggests something, 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"). Meaning "a trace (of something)" is attested from 1530s.
"make a sharp noise with the lips," 1550s, probably of imitative origin (see smack (v.2)). With adverbial force, "suddenly, directly," from 1782; extended form smack-dab is attested from 1892, American English colloquial (slap-dab is from 1886).
"to slap a flat surface with the hand," 1835, from smack (n.) in this sense; perhaps influenced by Low German smacken "to strike, throw," which is likely 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").
mid-13c., "to smell (something"); mid-14c., "to taste (something), perceive by taste" (transitive); late 14c. "to have a taste, taste of" (intransitive), from smack (n.1). Compare Old English smæccan "to taste," 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 ... (first attested 1590s). "Commonly but erroneously regarded as identical with [smack (n.2)], as if 'taste' proceeds from 'smacking the lips.'" [Century Dictionary]
"smart, sharp sound made by the lips," 1560s, from smack (v.1). Meaning "a loud kiss" is recorded from c. 1600. Meaning "sharp sound made by hitting something with the flat of the hand" is from c. 1746.
single-masted sailboat, 1610s, probably from Dutch or Low German smak "sailboat," perhaps from smakken "to fling, dash" (see smack (v.2)), perhaps so-called from the sound made by its sails. French semaque, Spanish zumaca, Italian semacca probably are Germanic borrowings.
"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)).