I think it comes from Heraldry where the bird is shown with legs and wings stretched out
Nov 12 2003, 6:31 AM
McGruff
Answer has 5 votes
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McGruff 25 year member
3694 replies
Answer has 5 votes.
Currently voted the best answer.
Websters Online says:
Main Entry: [2]spread-eagle
Function: adjective
Etymology: from the spread eagle on the Great Seal of the U.S.
Date: 1858
: marked by bombast and boastful exaggeration especially of the greatness of the U.S.
