Meaning

noun a blow from a flat object (as an open hand)

noun the act of smacking something; a blow delivered with an open hand

verb hit with something flat, like a paddle or the open hand

originFrom Middle English slappen, of uncertain origin, possibly imitative. Compare Low German Slappe (“slap”), whence also German Schlappe (“defeat”). Compare also Italian sleppa (“slap”).

Etymology from Wiktionary, CC BY-SA 3.0