See also fill-horse s.v. FILL sb.2 [f. THILL1 + HORSE.] The shaft-horse or wheeler in a team.
c. 1325. Gloss. W. de Bibbesw., in Wright, Voc., 168. En lymouns [gl.] thilles va ly limounere [gl.] the thillo-hors.
c. 1425. Voc., in Wr.-Wülcker, 665/32. Hic uiredus, thylhors.
1483. Funeral Edw. IV., in Lett. & Pap. Rich. III., etc. (Rolls), I. 7. Upon the fore horse, and the thil horse sat ij chariot men.
1543. Will J. England (Somerset Ho.). Oon Carte, a Tyll horsse & foure Oxen.
1704. W. Derham, in Phil. Trans., XXV. 1583. The Thill-Horse in Charless Wain, called Alioth.
1876. Browning, Pacchiarotto, xxi. A Spare-Horse? Be rather a thill-horse.