Hamstring \Ham"string`\, n. (Anat.) One of the great tendons situated in each side of the ham, or space back of the knee, and connected with the muscles of the back of the thigh.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Hamstring \Ham"string`\, v. t. [imp. & p. p. Hamstrung; p. pr. & vb. n. Hamstringing. See String.]

To lame or disable by cutting the tendons of the ham or knee; to hough; hence, to cripple; to incapacitate; to disable.

So have they hamstrung the valor of the subject by seeking to effeminate us all at home. --Milton.

Source: Webster's Revised Unabridged Dictionary (1913)