Merriam-Webster's Collegiate® Dictionary, 11th Edition
MISUSE
I. transitive verb
Etymology: Middle English, partly from mis- + usen to use; partly from Middle French mesuser to abuse, from Old French, from mes- + user to use
Date: 14th century
to use incorrectly ; misapply , abuse , mistreat , misuser noun
II. noun
Date: 14th century
incorrect or improper use ; misapplication