late 14c., "to refuse to praise" (a sense now obsolete), from Old French desalouer "to blame," from des- "not, opposite of" (see dis-) + alouer (see allow). Meanings "to reject, refuse to receive or acknowledge," also "refuse to allow, refuse to approve or sanction" are from c. 1400. Related: Disallowed; disallowing; disallowance.
