Thanks for thinking I'd have "the" answer but I don't. I think you'd almost have to look at how each "popular" bore size evolved, case-by-case basis, and 37mm is probably a good example.
From a website I linked below:
From the nineteenth century up to the end of the Second World War, 37mm was a common calibre in military service. This occurred because an international agreement, the Declaration of St Petersburg in 1868, banned explosive shells weighing less than 400 grams (just under one pound), for which 37mm was then the appropriate minimum calibre.
The Hotchkiss 1-pounder cartridge as used in the Hotchkiss 5-barrel revolving guns ca. 1880's is a good case in point. That was one of the first rifled breechloading guns to use that cartridge, and in fact the cartridge may have been developed by Hotchkiss (then a French company.) The caliber was variously known as "one pounder," "37mm," and (US Navy) "1.457 inch." This round became very popular because even with a black powder filler in the projectile, you could have an explosive projectile which was a good anti-personnel round at fairly long ranges, say one kilometer. The idea of course was to hit field works, fortification embrasures, or shipboard structures to wound or kill people nearby. Every arms maker in the world, more or less, came out with their own version of the 37mm single-barrel, "rapid-fire" naval deck gun in the 1880's-1890's, and they played a significant role in the Spanish-American War. Many single-barrel one-pounder/37mm guns were used in WWI as anti-machine-gun-nest sniping weapons, and as light tank armament. After WWI, many 37mm anti-tank guns were developed in many countries.
The cartridge collectors, and the arms industry refer to all metallic cartridges by the metric bore diameter and cartridge length in mm. Here's more info on 37mm history etc.
http://www.quarry.nildram.co.uk/37-40mm.htm The metric cartridge designation goes like this, one example in the popular 30mm size is "30 x 173mm" which happens to be the particular size and shape of cartridge used by the "GAU-8" 7-barreled Gatling gun carried by the A-10 "warthog" attack aircraft. That kind of designation helps avoid confusion with another very similar but non-interchangeable round used by the Brits, the "30 x 170mm" they use in their main gun on their armored fighting vehicles. The cartridge cases for the 30x170 are always made of aluminum in the US, and the 30x170 cases are always made of brass in the UK. Various other countries manufacture either of those cartridge cases in steel for their own specific weapons.
