Green’s Dictionary of Slang

1. a wig.

1977		D. Powis Signs of Crime 204: Syrup (of figs) Wig (term originates from the name of a commercial laxative). A common criminal expression, as wigs are not infrequently used as disguises and are often worn by prostitutes.
1992		Guardian 12 Nov. 26/4: During National Syrup Week I had to get a special DIY cutout wig.
2001		M. Coles Bible in Cockney 48: They weren’t like judges are today, people who sit in courts wearing funny-looking syrups!
2018		Napa Valley Register (CA) 22 Oct. C5/1: Roger gave me a list of some of his favorite words [...] syrup of fig — a wig.
2020		Twitter 20 Oct. 🌐 Syrup down in Charlton Park. Didn’t think it was that windy.

2. (Aus., also syrup of fig) an eavesdropper [rhy. sl. = fizgig n.² ].

1983

R. Aven-Bray Ridgey-Didge Oz Jack Lang 10: Being a syrup of fig was not his go. It was always on the cards that he could end up with a bit of swish if he got sprung being a gig.

3. an important person; a performance; a cigarette, a swig of liquor .

1998

‘World of Pub’ BBC Mar. [radio script] I’ll get in touch with a few large syrup of figs, that is bigwigs, see if they have bands doing syrup of figs, gigs, offer them them some syrup of figs, digs, suply them with syrup of figs, cigs, give ’em booze, they can have a few syrup of figs, swigs.