insinuate [E16th] This word was first used in legal contexts in the sense ‘enter (a document) on the official register’. Latin insinuare ‘introduce tortuously’ is the source, from in- ‘in’ and sinuare ‘to curve’, from sinus ‘a bend’ found in the sine of mathematics, sinuous, and the sinus (all late 16th century). Nearly all the English senses were already in Latin.