Green’s Dictionary of Slang

dookering n.

also dookin’, duckering, dukkering
[Rom. dukker, to tell fortunes]

(gypsy and tramp) fortune-telling; thus ducker v.

[UK]H. Brandon Dict. of the Flash or Cant Lang. 162/2: Dookin – fortune-telling.
[UK]Hotten Dict. of Modern Sl. etc.
[UK]Hotten Sl. Dict.
[UK]Sl. Dict.
[Scot]A. McCormick Tinkler-Gypsies of Galloway 232: Mrs C---’s dukkerin’ tan (fortune-telling tent). [Ibid.] 247: G-- was deputed to attend to customers in the dukkerin’ tan (fortune-telling tent).
[UK]J. Ware Passing Eng. of the Victorian Era.
[UK]P. Manning ‘Sl.’ in Kray (1989) 62: When a gypsy chy goes out duckering, she will read the palm of your hand.
[UK]D. Mitchell Black Swan Green 304: Books never taught a man to mong or ducker.
E. Petulengro Caravans & Wedding Bands 18: Our dukkering (palm reading) place was actually Mummy’s flat.
[US]W. Keyser ‘Carny Lingo’ in http://goodmagic.com 🌐 Dukkering — Gypsy fortunetelling.

In compounds