Gnast

From Middle English gnast, knast, from Old English *gnāst (“spark”) (attested in fȳrgnāst (“spark of fire”)), from Proto-Germanic *gahnaistô (“spark”), from Proto-Germanic *ga- + Proto-Germanic *hnaistô (“spark”), perhaps from the ultimate (imitative) source of German knistern (“to crackle”). Cognate with German dialectal Ganster (“spark”), Danish gnist (“spark, sparkle”), Swedish gnista (“spark”), Icelandic gneisti, neisti (“spark”), German Gneis (“spark, gneiss”) (whence English gneiss).

From Middle English gnasten, gnaisten, from Old English *gnǣstan, from Proto-Germanic *gnaistijaną, causative of *gnīstijaną (“to grind”), from Proto-Indo-European *gʰneydh-, *gʰneyd- (“to gnaw, scratch, rub”). Cognate with Saterland Frisian knasterje (“to gnash”), German Low German gnatschen (“to knead, gnash”), German knastern (“to gnash”), Icelandic gnesta (“to crack”).