I name my units before a big offensive. Normally I got two armies, sometimes 3 in late game, so they get named acoording the the direction of their attack, N, S, or E, W.
Followed by a number, counting from 1 upwards, I got up to 152 in my last warmongering game.
Followed by a letter to discribe it's function, D for defensive, S for spearhead, and M for units with Medic promotions, and nothing if it's just a normal attacker.
So a typical unit would be N31S for: Army group North; 31st unit to be named; and Spearhead meaning it has quite a few promotions.
It's quite something when you look back near the end of the game. Oh, I reserve 7, 27 and 38 for my best units. 7 for 7th Panther division in WWII; 27th Corps PR china; and 38th Corps PR China.
It doesn't take as long as it sounds, just a couple of minute counting numbers.
As for navy, snack names: HMS Rolo, HMS Mars, USS Walkers, USS Pepperoni......