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to know sb/sth inside out
01
to have very good knowledge or understanding about someone or something
What is the origin of the idiom "know someone or something inside out" and when to use it?
The idiom "know someone or something inside out" suggests an in-depth understanding or familiarity with a person, object, or subject. It implies knowing every detail, characteristic, or aspect thoroughly, as if one has explored its inner workings. This expression is used to emphasize a high level of knowledge, expertise, or familiarity with someone or something. It signifies that the individual has a comprehensive understanding, leaving no hidden aspects or mysteries.
Example
Having grown up with him, I know my brother inside out.
After years of studying this topic, I know it inside out.
She's worked with this software extensively and knows it inside out.
