One who holds and distributes what a company needs to keep going. The quartermaster fights nothing and everything depends on them.
English compound of quarter (Old French quartier, from Latin quartus, a fourth part) and master (Latin magister, one who is greater, a chief); the quartermaster's naval and military duty was originally the keeping of a ship's quarters and stores, from which the wider sense of supplying a company grew.
One who holds and distributes what a company needs to keep going. The oldest duty named in the word — keeping the stores in order — is still the whole job: nothing glamorous, and everything depends on it being done.