I’ve seen a good deal of pontificating about alignment languages over the years on forums and blogs; seems silly to me.
What usually gets overlooked is the glorious expediency of the concept of Common as a language spoken throughout a campaign world. As anyone who has run a globe-spanning campaign set in a historical era of our world can tell you, it is a huge pain to juggle who can understand what based on where the players are and where they’re from. The presence of a Common tongue in a game setting side-steps all of that, giving a baseline of communication that lets you get on with the game.
But where does Common come from? It seems miraculous, really, so why not give it a miraculous origin? Here’s how I explained the existence of Common in my Ulverland setting, and how I plan on explaining it in Scarabae as well:
Every civilized man and woman in the world speaks the Common tongue because of the existence of the Lexicos Spire. Long ago the Spire was erected by wise Matriarchs who performed a ritual upon it that grants the world’s denizens knowledge of a shared language. Unfortunately, this shared language has done little to end factionalism and war as the Matriarchs had hoped it might.
(Obviously inspired by the Tower of Babel.)