Wearing the pants
Being in charge, especially refers to women who are dominant over their husbands. In days of yore at least, men were supposed to be both the dominant force in the family and be the only family member to wear trousers. Thus a woman who wore trousers was considered to be in domineering.

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Email: You may be right to say that this refers to "domineering" women, but probably wrong to say that women wearing pants were once considered domineering. This phrase tells us about the marital relationship and not the persons to which it was applied. Fifty years ago it was just becoming acceptable for women to wear pants. In most marriages, it would have been clear that the man wore the pants no matter who dominated the relationship. "Who wears the pants?" is a not so subtle reminder to the wife that she observe the customary understanding of deferring to her husband on some matter of importance. I think if a woman is truly domineering, this has very little to do with what she wears. This phrase would not be for men who are faint of heart, but actually able to back it up by...wearing the pants so to speak.

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