trembling

Concise Oxford English Dictionary © 2008 Oxford University Press:
tremble/ˈtrembl/

▶verb shake involuntarily, typically as a result of anxiety, excitement, or frailty.

■ be in a state of extreme apprehension.

■ (of a thing) shake or quiver slightly.

▶noun a trembling feeling, movement, or sound.

– phrases
all of a tremble informal extremely agitated or excited.

– derivatives
trembling adjective,
tremblingly adverb,
trembly adjective (informal).

– origin ME: from OFr. trembler, from med. L. tremulare, from L. tremulus (see tremulous).