"quality of being in all places simultaneously," c. 1600, from Medieval Latin omnipraesentia, from omnipraesens "present everywhere," from Latin omnis "all, every" (see omni-) + praesens "present" (see present (adj.)).
word-forming element meaning "all," from Latin omni-, combining form of omnis "all, every, the whole, of every kind," a word of unknown origin, perhaps literally "abundant," from *op-ni-, from PIE root *op- "to work, produce in abundance."
c. 1300, "being in the same place as someone or something;" early 14c., "existing at the time," from Old French present "evident, at hand, within reach;" as a noun, "the present time" (11c., Modern French présent) and directly from Latin praesentem (nominative praesens) "present, at hand, in sight; immediate; prompt, instant; contemporary," from present participle of præesse "be before (someone or something), be at hand," from prae- "before" (see pre-) + esse "to be" (from PIE root *es- "to be").
Meaning "abiding in a specified place" is from mid-14c. in English. As a grammatical tense expressing action or being in the present time, recorded from late 14c.
<a href="https://www.etymonline.com/word/omnipresence">Etymology of omnipresence by etymonline</a>
Harper, D. (n.d.). Etymology of omnipresence. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/omnipresence