One of the mysteries of the English language finally explained.
When not engaged in or occupied with one's regular work; away from normal duties.
A period off-duty; time spent off-duty.
Of persons: not engaged in or occupied with regular work, not on duty. Also of things, actions, etc.: relating to or suggestive of this state.
Late 18th century; earliest use found in George Washington (1732–1799), revolutionary army officer and president of the United States of America. From off + duty.
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