Green’s Dictionary of Slang

dup v.

[dub v.1 or SE do up, although this would imply closing, unless the image is of fastening the door]

(UK Und.) to open (a door).

implied in dup the jigger
[UK]Shakespeare Hamlet IV v: Then up he rose, and donn’d his clothes, And dupp’d the chamber door.
[UK]Dekker ‘Canters Dict.’ Eng. Villainies (9th edn).
[Ire]Head Eng. Rogue I 49: Dup, To enter.
[UK]B.E. Dict. Canting Crew n.p.: Dup To enter or go into an house, As Dup the ken, Enter the House, Dup the Boozing-Ken, and booz a gage, go into the Alehouse and drink a pot.
[UK]Coles Eng. Dict.
[UK]A. Smith Lives of Most Notorious Highway-men, etc. (1926) 205: Dup, to enter, or open the door.
[UK]New Canting Dict. [as cit. c.1698].
[UK]Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
[UK]Scoundrel’s Dict. 17: To enter a House – Dup.
[UK]Grose Classical Dict. of the Vulgar Tongue.
[UK]Lex. Balatronicum.
[UK]Egan Grose’s Classical Dict. of the Vulgar Tongue.

In phrases

dup the jigger (v.) (also dup the gibber, dup the gigger) [gigger n.1 /jigger n.1 (1)]

(UK Und.) to open a door (cf. dub the gigg(er) under dub v.1 ).

[UK]Harman Caveat for Common Cursetours in Viles & Furnivall (1907) 84: dup the gyger to open the doore.
[UK]Groundworke of Conny-catching n.p.: Tower ye, yonder is the ken, dup the giger and maunde that is beneship.
[UK]Dekker Belman’s Second Nights Walk B2: If we [...] dup the giger of a Country coves Ken, to the quier cuffin we bing.
[UK]Rowlands Martin Mark-all 38: Dup the gigger, open the doore.
[UK]Dekker ‘Canting Song’ in Eng. Villainies (8th edn) O: [as cit. 1608].
[UK]T. Randolph Hey for Honesty III i: I’ll stand the pad [...] Nip bungs, dupp gibbers leager, louse and bouse.
[Ire] ‘The Beggars Curse’ Head Canting Academy (1674) 14: [as cit. 1608].
[UK]B.E. Dict. Canting Crew n.p.: Dup the giger open the doore.