-ioursuffix

a compound suffix, viz. -our suffix (Old French -ur, -or, French -eur), preceded by an i representing i, ei, e, of another element; as in saviour, Middle English and Anglo-Norman sauveour, Old French sauve-ur, -e-or, early Old French salvedur:—Latin salvātōrem; later French sauveur; in some cases a corruption of a different suffix, as in haviour, behaviour: see -our suffix. Through the general later change of -our to -or, and the confusion of this with -er, several words formerly in -iour are now written -ior (as warrior), -ier (as currier, soldier).