In the early 1960s, a pilot mistook a WW2 airfield for Heathrow, and landed his 707 on it, barely stopping before the end of the runway.
The runway being too short to lift a 707, mechanics stripped everything out of it they could to reduce the weight - seats, interiors, etc. They put barely enough gas in it to hop over to Heathrow, and managed to get it there safely.
I've lived 22 years of my life in the UK and 12 in North America and never heard of this before so I don't think it can be particularly common. I've heard of being 'laid off', 'fired', 'let go', 'terminated', 'made redundant', 'purged', but never this. Based on this link https://en.wikipedia.org/wiki/Cashiering it might be a military way of saying it so perhaps the poster has some background in that field.
I have never heard the usage of this word - I assumed the commenter was inventing a probably-understandable, slightly humorous usage on the fly which I've found to be a fairly common habit among ultra-intelligent people.
A few years back when SFO was closed after the Asiana crash, a lot of big planes got re-routed to Oakland, then once SFO was open again they made the hop across the Bay.
The runway being too short to lift a 707, mechanics stripped everything out of it they could to reduce the weight - seats, interiors, etc. They put barely enough gas in it to hop over to Heathrow, and managed to get it there safely.
The pilot who landed there was cashiered.