What is the meaning of Sinew?

A cord or tendon of the body.

A cord or string, particularly as of a musical instrument.

Muscular power, muscle; nerve, nervous energy; vigor, vigorous strength.

That which gives strength or in which strength consists; a supporting factor or member; mainstay.

A nerve.

To knit together or make strong with, or as if with, sinews.

Source: wiktionary.org