A tendon or sinew is a tough band of fibrous connective tissue, attached on one end to a muscle and on the other to a bone. They are similar to ligaments except that ligaments join one bone to another.
Due to their poor blood supply, tendons and ligaments are very slow to heal if injured, and never regain their original strength. This is why dislocations are more likely to occur at joints that have been dislocated in the past.
The Achilles tendon is a particularly large tendon connecting the heel to the muscles of the calf. It is so named because the mythic hero Achilles was killed due to an injury at this spot.
Tendon is also the name of a commune in the Vosgesdépartement in France.
Artificial sinew has an added benefit in that it is generally easier to hide a 'join', than some other materials, should an extra length be needed.
Wrap the length of sinew on an empty sewing thread spool or a short length of large-diameter dowel rod.
By first carefully wrapping the sinew flat on the spool, the twisting problem is remedied, and provides the added benefit of greater leverage while pulling the length taut as it is used.