dra·goon / drəˈgoōn/ • n. a member of any of several cavalry regiments in the household troops of the British army. ∎  hist. a mounted infantryman armed with a short rifle or musket.• v. [tr.] coerce (someone) into doing something: she had been dragooned into helping with the housework.ORIGIN: early 17th cent. (denoting a kind of carbine or musket, thought of as breathing fire): from French dragon ‘dragon.’

dragoon †carbine, musket, so called from its ‘breathing fire’ like a dragon; cavalry soldier, orig. applied to mounted infantry armed with this weapon. XVII. — F. dragon DRAGON; see -OON.
Hence vb. set dragoons upon, force rigorous measures upon. XVII.

Dragoon

DRAGOON. A mounted infantryman who, strictly speaking, rode his horse into battle but dismounted to fight, as opposed to a cavalryman, who was supposed to fight on horseback. He got this name from the primitive firearm, called a "dragon" because flame came from its mouth, with which the original dragoons were armed. Since dragoons could fight on horseback and cavalry could fight dismounted, the two names generally were used synonymously.