One of the mysteries of the English language finally explained.
A (male) teacher of horse riding and the management of horses, a riding instructor; (Brit. Army) an officer in charge of the instruction of troopers in a cavalry regiment.
Mid 17th century; earliest use found in Robert Stapleton (d. 1669), translator and playwright. From riding + master.
riding master/ˈrʌɪdɪŋ ˌmastə//ˈrʌɪdɪŋ ˌmɑːstə/
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