noun
Often used in the phrase 止めどなく (endlessly, without stopping) or 止めどがない (there is no end to it). Refers to a point where something stops or ceases.
彼の話は止めどがなかった。
His story had no end.
涙が止めどなく流れた。
Tears flowed endlessly.
限り is a more general word for 'limit' or 'as long as', while 止めど specifically refers to a stopping point or end, often used in set phrases.
Compound of 止め (tome, 'stopping') + ど (do, 'place' or 'point'). The exact derivation of ど is uncertain; it may be related to 所 (tokoro) or an old locative suffix.