late 14c., "not owing or payable; unjustly demanded," also "not appropriate, unseasonable," also "excessive," from un- (1) "not" + past participle of due (v.). Formed on model of Old French indeu, Latin indebitus.
an undue loan
I didn't want to show undue excitement
accused of using undue force
desire for undue private profit
his dress stops just short of undue elegance