as·sure / əˈshoŏr/ • v. [tr.] 1. tell someone something positively or confidently to dispel any doubts they may have: Tony assured me that there was a supermarket in the village. | [tr.] they assured him of their full confidence. ∎  make (someone) sure of something: you would be assured of a fine welcome.2. (often be assured) make (something) certain to happen: victory was now assured.DERIVATIVES: as·sur·er n.

assure XIV. — OF. asseūrer (mod. assurer) :- Rom. *assēcūrāre, f. AS- + sēcūrus SECURE.
So assurance XIV.