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general::
What's done is done; don't worry about the past, especially past errors or grievances. For example, Bill and Tom shook hands and agreed to let bygones be bygones. [First half of 1600s] let daylight through or into Shoot or stab a person, especially fatally. For example, Stick up your hands or I'll let daylight through you. This idiom alludes to making a hole in someone's body. [Slang; early 1700s]
American Heritage Idioms
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Phrase(s): Let bygones be bygones.
Cliché Forgive someone for something he or she did in the past. • Jill: Why don’t you want to invite Ellen to your party? Jane: She was rude to me at the office picnic. Jill: But that was six months ago. Let bygones be bygones. • Nancy held a grudge against her teacher for a long time, but she finally decided to let bygones be bygones.
McGrawhill's American Idioms And Phrasal Verbs