doctorbadwolf
Heretic of The Seventh Circle
They really don't, they're 180 off in some cases, like Sorcerer, the RL definition of which has nothing to do with inborn natural power and throwing elemental or wild magic around - though it is plenty negative.
So, there's no need for D&D class names to tightly match RL definitions - because no D&D class has ever done so.
Or, maybe you're just projecting what it means to you. I think anyone possibly into D&D has probably encountered it in fantasy and similar contexts. There are a number of definitions, but a key aspect of them is that they do not imply authority, or position in a military hierarchy - rather, the warlord exercises power, due to their ability to "mobilize loyal armed troops." The power of the D&D warlord, likewise, comes from his allies, not from any external authorities - a support character.
Is still, inescapably, a common military rank that implies authority over subordinates, and being subject to the orders of higher ranks. Which is in no way what the class is.
OTOH, the class is mostly about the skills/talents/abilities/tropes of the concept, not the position, it's broader than, but can easily encompass, military commanders and the like with external authority - just also with those abilities.

Okay, Tony, whatever helps you hold on to the edition war