To be indebted to someone.
To constrain someone by force or by social, moral or legal means.
To do (someone) a service or favour (hence, originally, creating an obligation).
To force someone to give (something), usually truth, or money.
To squeeze (wet clothing or cloth), either by twisting with one's hands, or by passing it through a wringer, to remove the water.
To push (an aircraft) to its performance limits; to push the envelope.