Non Omittas
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
A clause usually inserted in writs of execution, in England, directing the sheriff "not to omit" to execute the writ by reason of any liberty, because there are many liberties or districts in which the sheriff has no power to execute process uniess he has special authority.
2 Steph. Comm. 630.