Meaning

noun someone who believes and helps to spread the doctrine of another

adjective sticking fast

originEtymology tree Proto-Indo-European *h₂éd Proto-Italic *ad Proto-Italic *ad- Latin ad- Latin haereō Latin adhaereō Latin adhaerēnsder. Old French adherentbor. Middle English adherent English adherent From Middle English adherent, from Old French adherent, from Latin adhaerēns, present participle of adhaereō (“to stick to, cling”).

Etymology from Wiktionary, CC BY-SA 3.0