jimmy rounds, n. — Green’s Dictionary of Slang

jimmy rounds n.

[Fr. je me rends, the cry supposedly offered by hapless French sailors when faced with the might of the RN; however the Sporting Mag. (Oct. 1800) suggests an infantry encounter in Holland]

Frenchmen.

1800		Sporting Mag. Oct. XVII 39/1: An officer, in the Expedition to Holland, obliged to surrender to a superior party of the enemy, called out, Je me rends, i.e. I surrender. From that time the soldiers ludicrously called him Jemmy Round.
1909		J. Ware Passing Eng. of the Victorian Era 160/1: Jimmy Rounds (Nelsonic Period). Frenchmen – according to the Jack Tar of the wars with France in Nelson’s time. From the cry of the French sailor when face to face with the English mariner – je me rends.