- quack (v.)
- "to make a duck sound," 1617, quelke, of echoic origin (cf. M.Du. quacken, O.C.S. kvakati, L. coaxare "to croak," Gk. koax "the croaking of frogs," Hitt. akuwakuwash "frog"). M.E. on the quakke (14c.) meant "hoarse, croaking."
- quack (n.)
- "medical charlatan," 1638, short for quacksalver (1579), from Du. kwaksalver, lit. "hawker of salve," from M.Du. quacken "to brag, boast," lit. "to croak" (see quack (v.)) + zalf "salve." Cf. Ger. Quacksalber, Dan. kvaksalver, Swed. kvacksalvare.