Is it ensure, insure, or assure?
"military engine for hurling stones," mid-13c., from Old French mangonel "catapult, war engine for throwing stones, etc." (Modern French mangonneau), diminutive of Medieval Latin mangonum, from Vulgar Latin *manganum "machine," from Greek manganon "any means of tricking or bewitching," from PIE *mang- "to embellish, dress, trim" (cf. Old Prussian manga "whore," Middle Irish meng "craft, deception"). Attested from c.1200 in Anglo-Latin.