word-forming element meaning "not, opposite of, without" (also im-, il-, ir- by assimilation of -n- with following consonant, a tendency which began in later Latin), from Latin in- "not," cognate with Greek an-, Old English un-, all from PIE root *ne- "not."
In Old French and Middle English often en-, but most of these forms have not survived in Modern English, and the few that do (enemy, for instance) no longer are felt as negative. The rule of thumb in English has been to use in- with obviously Latin elements, un- with native or nativized ones.
mid-15c., saciaten, "fill to repletion, satisfy, feed or nourish to the full," from Latin satiatus, past participle of satiare "fill full, satisfy," from satis "enough" (from PIE root *sa- "to satisfy"). By 1620s in a bad sense, "to fill beyond or over natural desire, weary by repletion." Related: Satiated; satiating.
<a href="https://www.etymonline.com/word/insatiate">Etymology of insatiate by etymonline</a>
Harper, D. (n.d.). Etymology of insatiate. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/insatiate