Green’s Dictionary of Slang

a womanizer, a promiscuous man; 19C use, a man about town.

1531		J. Bellenden Boece I 184: Fydlaris, rutouris, huremasteris, & sportouris.
1593		Passionate Morrice (1876) 95: Now, fie of all the Beadles of Bridewell, if they spare such a sporter comming vnder their correction.
1854		Life in Boston & N.Y. (Boston, MA) 13 May n.p.: [They] are sporters of the first magnitude. We cannot see how he cn pay for champagne two or three times a week [...] on five dollars a week.
1855		Broadway Belle (NY) 29 Jan. n.p.: The sporters all do buy it / Just to read the fancy news.
1861		N.E. Police Gaz. (Boston, MA) 12 Oct. 5/4: Can some cheap sporter inform us whether Frank Porter receives her grass widow’s allowance since Jack went to the war?