Meaning

noun a rampart built around the top of a castle with regular gaps for firing arrows or guns

noun the action of constructing ramparts with gaps for firing guns or arrows

originFrom crenellate + -ion (suffix indicating an action or process, or its result). Crenellate is derived from French créneler (“to form the shape of a crenel, crenellate”), from Old French crenel (“crenel, embrasure”) (modern French créneau) (from Latin *crēnella, diminutive of crēna (“incision; notch”); compare Old French cren (“a notch”)) + -er (suffix forming infinitives of first conjugation…

Etymology from Wiktionary, CC BY-SA 3.0