Tried hard to do something; made a serious effort or attempt, especially at something difficult.
From Old French 'en- + devoir' (to put oneself in duty), with 'devoir' from Latin 'debere' (to owe). The meaning evolved to mean 'to try earnestly' by the 16th century.
Astronauts on space missions have code names for their spacecraft—one famous one was the Space Shuttle Endeavour, named after Captain Cook's ship and chosen because 'endeavor' means tireless effort toward an impossible goal.
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