Is it ensure, insure, or assure?
1580s, "frequently met with," from Latin obvius "that is in the way, presenting itself readily, open, exposed, commonplace," from obviam (adv.) "in the way," from ob "against" (see ob-) + viam, accusative of via "way" (see via). Meaning "plain to see, evident" is first recorded 1630s. Related: Obviously; obviousness.