that won't wash
idiom

- if an excuse or an argument will not wash, people will not believe it or accept it

(Cambridge Idioms Dictionary)

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In the Dictionary Of Catch Phrases, Eric Partridge suggests that the expression "that won't wash" originates from the idea that high-quality fabrics maintain their colours when put through the washing machine, while poor quality textiles tend to fade or wash out. So In a figurative sense, one can say that an argument, statement or situation "won't wash" if it won't stand up to scrutiny or examination.

For those who like their phrases and expressions clean, here are a few other examples:

- put someone through the wringer (in the past a wringer was used to press the water out of clothes after washing them = to make something difficult for someone (The teachers really put him through the wringer during the oral exams)

- come out in the wash = everything will work out, which alludes to removing clothes stains by washing them (Don't worry about it, it will all come out in the wash)

- don't wash your dirty linen in public = don't talk about your private problems in public (If you are going to agree to a newspaper interview, stay on topic and don't wash your dirty linen in public)

- washed out = exhausted (I can't go with you tonight. I'm all washed out)

- washed up = finished (He was once a famous musician, but he's washed up meanwhile)

- wash your hands of something = to end all involvement with something or someone (Instead of finishing the project, he just washed his hands of everything and left us holding the bag*)

*Bonus phrase - To leave someone holding the bag means to let someone take all the blame


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SYNONYMS

I don't buy that

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SMUGGLE OWAD into today's conversation

"That line of argument won't wash, we need to come up with a better one."