thrum

Imitative.

From Middle English thrum, throm (> Anglo-French trome), from Old English þrum (found in tungeþrum (“ligament of the tongue”)) from Proto-Germanic þrumą. Cognate with German Trumm, Trümmer and Old Norse þrǫmr (“edge, brim”), and more distantly to Latin termen.

Apparently a reduced form of the stem of threepenny/threepence through a sequence such as /ˈθrɛp(ə)n-/ > /ˈθrʊp(ə)m-/ > /ˈθrʊm-/ (> /ˈθɹʌm-/).