tremulousness

noun

1. (uncountable)The property or state of being tremulous.

   “"… 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.”

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