Is it ensure, insure, or assure?
late 14c., "ask, make inquiry," from Old French demander (12c.) "to request; to demand," from Latin demandare "entrust, charge with a commission" (in Vulgar Latin, "to ask, request, demand"), from de- "completely" (see de-) + mandare "to order" (see mandate). Meaning "to ask for as a right" is early 15c., from Anglo-French legal use. Related: Demanded; demanding.
late 13c., "a question," from Old French demande (see demand (v.)). Meaning "a request, claim" is from c.1300. In the political economy sense (correlating to supply) it is attested from 1776 in Adam Smith.