Is it ensure, insure, or assure?
1690s, from French contraster (Old French contrester), modified by or from Italian contrastare "stand out against, strive, contend," from Vulgar Latin *contrastare "to withstand," from Latin contra "against" (see contra) + stare "to stand," from PIE root *sta- "to stand" (see stet).
Middle English had contrest "to fight against, to withstand," which became extinct. Modern word re-introduced as an art term. Related: Contrasted; contrasting; contrastive.
1711, from contrast (v.).