Green’s Dictionary of Slang

Christian adj.

of things, ‘decent’, ‘respectable’ or ‘presentable’.

1818		W. Scott Legend of Montrose Ch. xiv: You must make the best disposition you can [...] for my taking the command, whilk I would have gladly done had you been to fight with any Christian weapons .
1846		D. Jerrold Mrs. Caudle’s Curtain Lectures 10: You should come home in Christian time, not at half-past twelve.
1890		‘Rolf Boldrewood’ Colonial Reformer III 35: What a brute that mare of yours is to amble, Tottie [...] can’t you make her go a more Christian pace?

SE in slang uses

In compounds

Christian pony (n.)

1. a sedan chair man.

c.1786		Grose Classical Dict. of the Vulgar Tongue ms. additions n.p.: Christian Poney a Chairman.
1788, 1796		Grose Classical Dict. of the Vulgar Tongue (2nd, 3rd edn).
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.

2. (Can.) a handcart man.

1984

Partridge DSUE (8th edn) 215/2: ca. 1860–1905.