Definition of "tremulousness"

"… now let us see what the boy has to say;” and he took the other letter, which was written in a great floundering boy’s hand, and sealed with the large signet of the Pendennises, even larger than the Major’s own, and with supplementary wax sputtered all round the seal, in token of the writer’s tremulousness and agitation.

1848 November – 1850 December, William Makepeace Thackeray, chapter 1, in The History of Pendennis. […], volumes (please specify |volume=I or II), London: Bradbury and Evans, […], published 1849–1850

He hates the wavering uncertainty in his voice, the tremulousness of it.

2020, Brandon Taylor, Real Life, Daunt Books Originals, page 250