get someone's number

get (one's) number

1. To obtain someone's phone number, often when there is a romantic interest between the two people. Oh please, there's no way you'll be able to get that hot girl's number.
2. To understand or know someone or something well enough to anticipate what they will do. Oh, don't worry, I've got his number—he's a typical brat.
See also: get, number
Farlex Dictionary of Idioms.

get someone's number

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]
See also: get, number
The American Heritage® Dictionary of Idioms by Christine Ammer.
See also:
  • cover
  • grab (someone or something) by the throat
  • grab someone by the throat
  • grab someone/something by the throat
  • get someone's dander up, to
  • help (someone) along
  • help along
  • die on
  • die on (someone or something)
  • die on someone