have (got) someone by the short and curlies
US /hæv ɡɑt ˈsʌm.wʌn baɪ ðə ʃɔrt ænd ˈkɜr.liz/
UK /hæv ɡɑt ˈsʌm.wʌn baɪ ðə ʃɔrt ænd ˈkɜr.liz/

1.
mieć kogoś w garści, trzymać kogoś za jaja
(informal, sometimes offensive) to have complete control over someone, especially by having an advantage over them or by knowing something about them that they want to keep secret
:
•
The company had him by the short and curlies after he signed that contract.
Firma miała go w garści po tym, jak podpisał ten kontrakt.
•
She knew his secret, so she had him by the short and curlies.
Znała jego sekret, więc miała go w garści.