have (someone) by (something)
To hold someone in place by grasping something, such as a body part or a piece of clothing (named after "by"). Tommy had the burglar by the throat when the police arrived. I had my brother by the sleeve and pulled him back into the house.
have someone by something
to hold onto someone by something. (See also someone by someone or something">have someone by someone or something.) She had me by the shoulder and I couldn't get away. Timmy had Billy by the collar and was punching him on the shoulder.