smackyoudaoicibaDictYouDict[smack 词源字典]
smack: English has four separate words smack. The oldest, ‘taste’ [OE], is now mainly used metaphorically (as in smack of ‘suggest’). It has relatives in German geschmack, Dutch smaak, Swedish smak, and Danish smag ‘taste’, and may be distantly linked to Lithuanian smagus ‘pleasing’. Smack ‘hit’ [16] at first meant ‘open the lips noisily’, and was borrowed from Middle Low German or Middle Dutch smacken, which no doubt originated in imitation of the noise made.

It was not used for ‘hit with the palm of the hand’ until the mid 19th century. The slang use of the derivative smacker for ‘money’ originated in the USA around the end of World War I. Smack ‘small sailing boat’ [17] was borrowed from Dutch smak, a word of unknown origin. And smack ‘heroin’ [20] is probably an alteration of schmeck ‘heroin or other drug’ [20], which in turn comes from Yiddish schmeck ‘sniff’.

[smack etymology, smack origin, 英语词源]
smack (n.1)youdaoicibaDictYouDict
"a taste, flavor, savor" especially a slight flavor that suggests something, from Old English smæc "taste; scent, odor," from Proto-Germanic *smak- (cognates: Old Frisian smek, Middle Dutch smæck, Dutch smaak, Old High German smac, German Geschmack, Swedish smak, Danish smag), from a Germanic and Baltic root *smeg- meaning "to taste" (cognates: Lithuanian smaguriai "dainties," smagus "pleasing"). Meaning "a trace (of something)" is attested from 1530s.
smack (n.4)youdaoicibaDictYouDict
"heroin," 1942, American English slang, probably an alteration of schmeck "a drug," especially heroin (1932), from Yiddish schmeck "a sniff."
smack (v.1)youdaoicibaDictYouDict
"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).
smack (n.3)youdaoicibaDictYouDict
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.
smack (v.2)youdaoicibaDictYouDict
"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 smagiu "to strike, knock down, whip").
smack (v.3)youdaoicibaDictYouDict
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]
smack (n.2)youdaoicibaDictYouDict
"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.