Is it ensure, insure, or assure?
c.1300, from Old French desputer (12c.) "dispute, fight over, contend for, discuss," from Latin disputare "weigh, examine, discuss, argue, explain," from dis- "separately" (see dis-) + putare "to count, consider," originally "to prune" (see pave).
Used in Vulgate in sense of "to argue, contend with words." Related: Disputable; disputed; disputing. The noun is not certainly recorded before 1590s (disputacioun in that sense is from late 14c.).