Endeavor is one of those nifty words in English that functions as both a verb and a noun. The standard definition of endeavor as a noun:

1. A conscientious or concerted effort toward an end; an earnest attempt.

2. Purposeful or industrious activity; enterprise.

The etymology is one of those sorts of interesting fossil word histories. Modern English endeavor is from Middle English endevour, from the Middle English verb endeveren, "to make an effort, from the Middle English (putten) in dever, "to put oneself" in duty, make it one's duty.

Now—and this is the really interesting part. You remember than in 1066 William the Conqueror from Normandy, part of modern day France, won the English crown at the Battle of Hastings. He and his followers—the ruling class of England for the next couple of hundred years—were speakers of Norman French, unlike the English peasants of the time, who mostly spoke Old English. English began to rapidly steal acquire lots of French loan words. The very early Middle English (putten) in dever, is a combination of good old Old English, with its use of the familiar to Modern English put plus the equally familiar preposition in, with the solidly Norman French dever, more recognizable in its modern French form, devoir, which roughly means "duty," or "must do," or "obligated." Devoir is of course derived from Latin L. debere "owe." The Middle English (putten) in dever a translated descendent of the same ancestor as modern French se mettre en devoir "do one's utmost," in that the French mettre has been translated quite literally to the English equivalent "put."