An Etymological Dictionary of Astronomy and Astrophysics

1. To declare earnestly to; inform or tell positively; state with confidence to.
   

2. To give confidence to; encourage.

Etymology (EN): M.E. as(e)uren, assuren, from O.Fr. aseurer, from L.L. assecurare, from as-, variant of → ad-, + secur-, → secure, + -a- thematic vowel, + -re infinitive suffix.

Etymology (PE): Âtenzidan, from â- intensive prefix, + tenz, → sure, + -idan infinitive suffix, → -ize.