Green’s Dictionary of Slang

monty n.

also full monty, monte
[ety. unknown; the success of the 1997 film The Full Monty hugely popularized the phr. and the variety of etys. for monty/monte were proposed, although none has been accepted as authoritative; they range from monte, a Sp. and US Hisp. game of chance, played with a pack of 45 cards, the tailor’s Montague Burton, i.e. a full three-piece suit; the ‘full English breakfast’ purportedly enjoyed by Field Marshall Montgomery, during WWII; the gambling town of Monte Carlo, in which the full monte would equate with ‘breaking the bank’ and several more]

1. everything, all that there is, ‘the lot’; esp. in phr. the full monty.

Stage & TV Today 30 Aug. 16: There was a fellow sitting there with the full monty on, big gold rings, all that.
[UK]Indep. 5 June 30: Each player has a specific training routine, and meals are carefully monitored. Muesli and fruit for breakfast – at least until the coach is absent, then it is the full Monty.
[UK]J. Cameron It Was An Accident 221: Where you been, who you clocked, who they get a meeting with, the monte.
[UK]J. King White Trash 67: He wasn’t finished, was going for the full monty.

2. see monte n.1 (2)

3. see monte n.1 (3)