dumbness (part of speech: noun)
taciturnity (part of speech: noun)
- This counted for nothing definite, of course; and as for the taciturnity of which the chambermaid complained, the ailments from which my poor friend was reported to have been suffering were quite enough to account for that. - "The House by the Lock", C. N. Williamson.
- The gravity and taciturnity of the nation have been ascribed to the effects of this proverb. - "Curiosities of Literature, Vol. 3 (of 3)", Isaac Disraeli.
- He thanked Heaven for the taciturnity of his companions. - "A Pagan of the Hills", Charles Neville Buck.