Green’s Dictionary of Slang

rug adj.3

[? the comfort and security provided by a rug, or corruption of SE right]

In phrases

all rug (adj.)

(UK Und.) everything is secure.

[UK] B.E. Dict. Canting Crew It’s all Rug, c. the Game is secured.
[UK] T. Lucas Lives of the Gamesters (1930) 176: His great dexterity, of making all Rugg at Dice, as the cant is for securing a die between two fingers.
[UK] in Anon. New Canting Dict. [as B.E.].
, , , in Bailey Universal Etymological English Dict. [as NCD 1725].
[UK], in Grose Classical Dict. of the Vulgar Tongue n.p.: It is all rug, all right and safe, the game is secure, (cant.
in G. Andrewes Dict. Slang & Cant.
[UK] in Lex. Balatronicum.
[UK] in Egan Grose’s Classical Dict. of the Vulgar Tongue.
[UK] G. Kent Modern Flash Dict. 28: Rugg - all right and safe.
[UK] in Flash Dictionary in Sinks of London Laid Open [as Kent 1835].
[US] in Matsell Vocabulum.