thiller

plural thillers

1. The horse that goes between the thills, or shafts of a carriage, and supports them.

   , And apron, and scissars for head and for tail, / Whole bridle and saddle, whitleather, and nall, / With collars and harness, for thiller and all […]

   1557 February 13 (Gregorian calendar), Thomas Tusser, A Hundreth Good Pointes of Husbandrie, London: […] Richard Tottel, →OCLC; republished London: […] Robert Triphook, […], and William Sancho, […], 1810, →OCLC

   1 more example

   [T]he middle of it [i.e., the thigh, is] the prop or thiller, the body the vveight, and the leg the povver; either of vvhich being brought by a ſharp angle to a dovvnright or perpendicular or more, vvith the thiller, vvill by ſo much leſſen the vveight, from the yielded aſſumption in that mechanick povver, That the point, vvhich is toucht by a perpendicular from the centre of heavineſs, is one of the terms: […]

   1674, N[athaniel] Fairfax, chapter V, in A Treatise of the Bulk and Selvedge of the World. Wherein the Greatness, Littleness and Lastingness of Bodies are Freely Handled. […], London: […] Robert Boulter, […], →OCLC, page 153

2. The last horse in a team.