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general::
Also, have someone's number. Determine or know one's real character or motives, as in You can't fool Jane; she's got your number. This expression uses number in the sense of "a precise appraisal." Charles Dickens had it in Bleak House (1853): "Whenever a person proclaims to you, ‘In worldly matters I'm a child,' . . . that person is only crying off from being held accountable . . . and you have got that person's number." [Mid-1800s] get someone wrong Misunderstand someone, as in I think you got him wrong. This expression is often put as Don't get me wrong, used to clarify one's feelings, views, or the like, as in Don't get me wrong? I'm happy about the outcome. [Colloquial; c. 1900] Also see MAKE NO MISTAKE.
American Heritage Idioms