Green’s Dictionary of Slang

1. one who has a dose of syphilis.

1590		Three Lords and Three Ladies of London J3: The French canker consume ye, you were an old Frenchman.
1619		J.T. Westminster Hunting of the Pox n.p.: Nor see that no obstructions be, or fragments let remaine, / For then there will a relaps call the French-man backe againe.

2. a scholar of French.

1670		C. Cotton Espernon Preface: The greater part of them being better Frenchmen, than I pretend to be [OED].
1828		Bentham in Works (1843) I 247: The subject was not without its difficulties; the language French: I am but a sorry Frenchman now; I was, I imagine, not quite so bad an one then .

3. see fransman n.