taciturnity

[L. taciturnitas: cf. F. taciturnité.]
Habitual silence, or reserve in speaking.

The cause of Addison's taciturnity was a natural diffidence in the company of strangers.

The taciturnity and the short answers which gave so much offense.

noun

The keeping of one's thoughts and emotions to oneself: control, reserve, restraint, reticence, self-control, self-restraint, uncommunicativeness. See restraint/unrestraint.

The noun has one meaning:

Meaning #1: the trait of being uncommunicative; not volunteering anything more than necessary
  Synonyms: reserve, reticence