Is it ensure, insure, or assure?
late 14c., "praise" (a sense now obsolete), from Old French aloance "allowance, granting, allocation," from alouer (see allow). Sense of "a sum alloted to meet expenses" is from c.1400. In accounts, meaning "a sum placed to one's credit" is attested from 1520s. To make allowances is literally to add or deduct a sum from someone's account for some special circumstance. Figurative use of the phrase is attested from 1670s.