If three people all have different terminal medical conditions, which are currently making their state of life excruciating, and will kill them shortly, and there is one healthy person who can be killed and their organs repurposed to restore quality of life and stop the medical condition to all of those people then utilitarianism says it is moral to do that.
Any answer saying that it is wrong to do that shows there must be a factor beyond need in the determination.
The practice became the standard for nomenclature starting in the 1920s, gradually replacing other conventions such as naming based on the year of adoption (M1911, M1919, and M1903 as examples). This led to a lot of M1s in WW2 due to the timing of the nomenclature change.
I find it interesting that the .30-06 caliber is named for year of adoption, with the name of the standard cartridge in WW2 being M1.