Farriery. [f. THOROUGH- + PIN sb.1 (cf. sense 10).) A swelling in the sheath of the tendon of the flexor perforans muscle in a horse’s hock, appearing on both sides so as to suggest a pin passing through; also a similar swelling in the carpal joint of the fore-leg. Cf. earlier through-serewe, etc.: s.v. THROUGH- 2.
1789. Bath Jrnl., 22 June, Advt., [A pony] with a spavin and thorough pins.
1831. Youatt, Horse, 265. We have spoken of wind-galls…. A similar enlargement is found above the hock…. As from its situation it must necessarily project on both sides of the hock, in the form of a round swelling, it is called a thorough-pin.
1906. Daily News, 20 April, 6. Amitie, a very well-bred mare, is marred by a thorough-pin.
