to move (something) with a short sudden pull, push, twist, or jolt
She jerked her head out of the way
(often + out) to say (something) in an abrupt or explosive manner
to make a sudden spasmodic motion
They jerked to attention
to move in a series of short abrupt motions
jerker noun
[prob alteration of English dialect yerk to thrash, attack, excite, from Middle English yerken to bind tightly, to lash; earlier history unknown]