The same set of poses and props (for instance, a minesweeper, a guy holding his rifle over his head with a bayonet, a spotter with one arm raised looking through binoculars, a guy about to place a shell inside a mortar, etc.) can be found in toys made (or at least sold) by several different companies, in stock art, in movies, there's even an army men font. What's the deal? I assume since they're mostly patterned after WW2 soldiers (And more elaborate sets often include British, Japanese, German, and sometimes even Russian figures) that they must have arisen sometime after the 1940s, but can anyone narrow it down, point to a specific manufacturer or even an individual creator?

Bonus question: Why are they so commonly referred to as "army men" rather than just as soldiers or whatever?

Edit: I'd also be interested in hearing any answers to the same questions for other stock plastic figurines (spacemen, cowboys and indians, dinosaurs, civil war soldiers, that sort of thing) which have similar standardized designs.