From a variant (influenced by whack) of Middle English thakken (“to stroke”), from Old English þaccian (“to touch gently, stroke, tap”), from Proto-Germanic *þakwōną (“to touch lightly”), from Proto-Indo-European *tag-, *taǵ- (“to touch”). Cognate with Old Dutch þakolōn (“to stroke”), Old Norse þykkr (“a thwack, thump, blow”), Icelandic þjökka, þjaka (“to thwack, thump, beat”), Norwegian tjåka (“to strike, beat”), Latin tangō (“touch”). More at tangent.
thwack (plural thwacks)
- The act of thwacking; a strike or blow, especially with a flat implement.
- To strike with a wet, slapping sound.