BUP

(Back UP) A backup file of the IFO file on a DVD, containing the information about the track, organization, menus, chapters, and subtitles on the disk. It is used as a redundant way to access information usually accessed by an IFO, in the event the disk is scratched or otherwise damaged.
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Bup

Bup is British slang for a slice of bread and butter.
Found on http://www.probertencyclopaedia.com/browse/ZBA.HTM
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