thrum

Concise Oxford English Dictionary © 2008 Oxford University Press:
thrum1

▶verb (thrums, thrumming, thrummed) make a continuous rhythmic humming sound.

■ strum (the strings of a musical instrument) in a rhythmic way.

▶noun a continuous rhythmic humming sound.

– origin C16: imitative.

Concise Oxford English Dictionary © 2008 Oxford University Press:
thrum2

▶noun (in weaving) an unwoven end of a warp thread, or a fringe of such ends, left in the loom when the finished cloth is cut away. ▶verb (thrums, thrumming, thrummed) decorate with thrums.

– origin OE thrum (only in tungethrum ‘ligament of the tongue’): of Gmc origin.