Plural of six; the number or card with six spots or points; can mean things in groups of six.
From Old English 'sex' and Latin 'sex,' both meaning the number six—one of the most ancient number words in human language.
The phrase 'at sixes and sevens' means confused or disorganized, and historians still don't agree on why—it might come from old dice games where throwing sixes and sevens caused disputes, or from military terminology where units got confused.
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