TITLE: Why the terminology "monoid"?
QUESTION [24 upvotes]: As I am not a native English speaker, I sometimes am bothered a little with the word "monoid", which is by definition a semigroup with identity. But why this terminology? 
I searched some dictionaries (Longman for English, Larousse for Francais, Langenscheidts for Dentsch) but didn't find any result, and it seems to me that it is just a pronounciable word with certain mathematical meaning. So, where does it come from? Is there any etymological explanation? Who was the first mathematician who used it?

REPLY [11 votes]: If Chevalley was the first to popularize the term "monoid", then I can pretty confidently guess that it meant the structure of operators on a single type (i.e., a category with a single object).  Note that Chevalley's second example (after the mandatory natural numbers) is the collection of mappings from a set to itself.  His term for the monoid operation is "composition."
The term "groupoid" in the sense of a category with invertible arrows was already well-established.  So, the use of "monoid" to mean a category of arrows on a single object seems quite natural.