get the wrong end of the stick

get hold of the wrong end of the stick

To misunderstand something. He must have gotten hold of the wrong end of the stick about something when I was talking to him earlier, because he has started acting really odd whenever I see him now.
See also: end, get, hold, of, stick, wrong
Farlex Dictionary of Idioms.

get the wrong end of the stick

or

get hold of the wrong end of the stick

INFORMAL
If someone gets the wrong end of the stick or gets hold of the wrong end of the stick, they completely misunderstand a situation or something that is said. You got the wrong end of the stick — I invited him to be kind, not because I fancied him! Did I get hold of the wrong end of the stick? Was that not what he meant?
See also: end, get, of, stick, wrong
Collins COBUILD Idioms Dictionary, 3rd ed.

get (hold of) the wrong end of the stick

misunderstand someone or something completely.
See also: end, get, of, stick, wrong
Farlex Partner Idioms Dictionary

get (hold of) the ˌwrong end of the ˈstick

(British English, informal) understand somebody/something in the wrong way: You’ve got the wrong end of the stick. He doesn’t owe me money, I owe him! OPPOSITE: get something right/straight
See also: end, get, of, stick, wrong
Farlex Partner Idioms Dictionary
See also:
  • a/the feel of (something)
  • (I) wouldn't (do something) if I were you
  • a straw will show which way the wind blows
  • a crack at (someone or something)
  • all right
  • (you) wanna make something of it?
  • all for the best
  • a thing of the past
  • a slew of (something)
  • a bird in the hand