The Collaborative International Dictionary
Omittance
Omittance \O*mit"tance\, n.
The act of omitting, or the state of being omitted;
forbearance; neglect.
--Shak.
Douglas Harper's Etymology Dictionary
omittance
"omission," c.1600, perhaps coined by Shakespeare, who used it in wordplay ("Omittance is no quittance"), from omit + -ance.
Wiktionary
omittance
n. the act of omitting something