c. 1300, "agree to, approve;" late 14c. "admit as true," from Old French assentir "agree; get used to" (12c.), from Latin assentare/adsentare, frequentative of assentire "agree with, approve," from ad "to" (see ad-) + sentire "to feel, think" (see sense (n.)). Related: Assented; assenting.
early 14c., "consent, approval," from Old French assent, a back-formation from assentir "to agree" (see assent (v.)). "Assent is primarily an act of the understanding; consent is distinctly the act of the will: as, I assent to that proposition; I consent to his going" [Century Dictionary].