Is it ensure, insure, or assure?
late 13c., anhaunsen "to raise, make higher," from Anglo-French enhauncer, probably from Old French enhaucier "make greater, make higher or louder; fatten, foster; raise in esteem," from Vulgar Latin *inaltiare, from Late Latin inaltare "raise, exalt," from altare "make high," from altus "high" (see old).
Meaning "raise in station, wealth, or fame" attested in English from c.1300. The -h- in Old French supposedly from influence of Frankish *hoh "high." Related: Enhanced; enhancing.