Perhaps best known from its use in Kipling's 'A Smuggler's Song':
'Five and twenty ponies trotting through the dark,
Brandy for the Parson, 'baccy for the Clerk,
Laces for a lady, letters for a spy,
So watch the wall, my darling
While the gentlemen go by'
although, at least in the version of the poem I have, it is written with an apostrophe, disqualifying it from Chi altogether!
Also commonly used (in UK at least) in the phrase 'wacky baccy' referring (usually) to cannabis.
Common? probably not - I certainly didn't see it in the 'cyberspace' game; at least it didn't cost me a rosette; I also missed 'peccary'!!
MK