From another question I found out that Australians and New Zealanders call lunch and snacks crib.
On the Macquarie dictionary site, there are several (user-contributed) theories about why, but nothing authoritative. These all seem to agree that it's a mining term likely from the Cornish dialect, but disagree as to its original meaning.
User067531 provided the link to Macquarie's in his answer here.
I was unable to find anything on Etymonline or elsewhere showing this derivation.