quaver

v. 1 (esp. Of a voice or sound) vibrate, shake, tremble. 2 sing or say with a quavering voice. n. 1 mus. Note half as long as a crotchet. 2 trill in singing. 3 tremble in speech.  quavery adj. [probably imitative]

v. i. To tremble; to vibrate; to shake.