from Latin Hibernia, the Roman name for Ireland, also in forms Iverna, Juverna, Ierne, etc., all ultimately from Old Celtic *Iveriu "Ireland" (see Irish (n.)). This particular form of the name was altered in Latin as though it meant "land of winter" (see hibernation).
word-forming element making nouns implying a practice, system, doctrine, etc., from French -isme or directly from Latin -isma, -ismus (source also of Italian, Spanish -ismo, Dutch, German -ismus), from Greek -ismos, noun ending signifying the practice or teaching of a thing, from the stem of verbs in -izein, a verb-forming element denoting the doing of the noun or adjective to which it is attached. For distinction of use, see -ity. The related Greek suffix -isma(t)- affects some forms.
<a href="https://www.etymonline.com/word/Hibernicism">Etymology of Hibernicism by etymonline</a>
Harper, D. (n.d.). Etymology of Hibernicism. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/Hibernicism