in Latin, the form of com- "together, with" in compounds with stems beginning in vowels, h-, and gn-; see com-. Taken in English from 17c. as a living prefix meaning "together, mutually, in common," and used promiscuously with native words (co-worker) and Latin-derived words not beginning with vowels (codependent), including some already having it (co-conspirator).
late 14c., "reality," from Old French existence, from Medieval Latin existentia/exsistentia, from existentem/exsistentem (nominative existens/exsistens) "existent," present participle of Latin existere/exsistere "stand forth, come out, emerge; appear, be visible, come to light; arise, be produced; turn into," and, as a secondary meaning, "exist, be;" from ex "forth" (see ex-) + sistere "cause to stand," from PIE *si-st-, reduplicated form of root *sta- "to stand, make or be firm."
<a href="https://www.etymonline.com/word/coexistence">Etymology of coexistence by etymonline</a>
Harper, D. (n.d.). Etymology of coexistence. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/coexistence