What is the real word origin for endeavor?

The word "endeavor" has its roots in Old French and ultimately comes from the Latin word "in" meaning "in" or "into" and "de" meaning "of" or "from", combined with the verb "avor" meaning "to desire" or "to be eager".

So, literally, "endeavor" means "to be eager about something" or "to put effort into something".

The word has been used in English since the 14th century, and it has evolved to mean "a serious attempt or effort".