Origin: French suffix -eur
Monsieur has 3 different meanings across 1 category:
used as a French courtesy title; equivalent to English `Mr'
"The waiter bowed politely and addressed me as monsieur before bringing out my menu."
A man, especially a French gentleman.
"The waiter bowed and addressed the man at the table as monsieur while bringing him the menu."
Mister, especially in a French context.