"Yeoman" is an antiquated term for farmers, tradesmen and other members of the early English middle class. The term suggests someone upright, sturdy, honest and trustworthy.
Yeoman is also a naval occupation, roughly equivalent to a secretary.
Yeomanry were the Territorialcavalry regiments of the British Army during the First World War though as the war progressed many regiments fought as dismounted infantry. Many of these regiments retained their "yeomanry" designations after the war, and through modern times.