Green’s Dictionary of Slang

1. a person or group who are especially well looked after when visiting an organization of kindred spirits.

[1855		Sun (Baltimore) 25 Oct. n.p.: A company of firemen from Rochester, N.Y. [...] continue to receive the attentions of their brother firemen of Baltimore [...] This evening the visiting firemen will be the guests of the Washington Hose Company].
1920		A. Baer Two & Three 27 Jan. [synd. col.] Reading from left to right, which is the usual procedure when identifying flashlight photographs of the visting firemen’s banquet.
1921		T.A. Dorgan in Zwilling TAD Lex. (1993) 93: Slipping the berry to the bird who wore the only full dress at the visiting fireman’s benefit.
1958		(con. 1890s) S.H. Adams Tenderloin 170: At suspiciously short intervals ‘visiting firemen,’ as out-of-town patrons were known, made the rounds of the houses.
1987		R. Campbell Alice in La-La Land (1999) 67: I thought you had some firemen visiting town.
2023		M. Herron Secret Hours 214: ‘Alison’s a visiting fireman [...] here to make sure there aren’t any cinders about to burst into flames’.

2. a tourist who is expected to spend freely.

1989		J. Morton Lowspeak.
2020		D. Winslow ‘Broken’ in Broken 16: She was about to make that much with a visiting fireman at the Roosevelt Hotel.

3. a parasite, a hanger-on.

1947

B. Schulberg Harder They Fall (1971) 190: The usual visiting firemen who manage to find their way to a winner’s dressing-room.