Webster's Revised Unabridged Dictionary · 1913

Tether

Tether (têt"ẽr) , noun

[Formerly tedder, Old English tedir; akin to LG. tider, tier, Icelandic tjōer, Swedish tjūder, Danish toir. r64.]

A long rope or chain by which an animal is fastened, as to a stake, so that it can range or feed only within certain limits.

Tether , transitive verb

To confine, as an animal, with a long rope or chain, as for feeding within certain limits.
And by a slender cord was tethered to a stone. — Wordsworth