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Also, A-1; A-number-one. First-class, of the best quality, as in This is an A-one steak. The term comes from Lloyd's, the British insurance company, which in its 1775 shipping register designated the condition of a ship's hull by a letter grade (A, B, etc.) and of its cables, anchor, and other equipment by a number grade (1, 2, etc.). By the early 1800s A-1, the best possible grade, was being transferred to anything of superior quality. In addition to the idiom beginning with APART, Also see COME APART; FALL APART; PICK APART; POLES APART; SET APART; TAKE APART; TEAR APART; TELL APART.
American Heritage Idioms