Iwas thinking this was mabey not an Army issue thing and the AF blivett came to mind.
It could be branch specific. Could even be a slang term that was unit specific. Being an ex-trucker, my mind first thought that a term that incorporated ‘camel’ would be a possibility. Like ‘camel bag’.
I did find a website that states ‘blivet’ is allegedly from traditional U.S. Army slang dating back to WW2, but no actual evidence was given.