Language History of the World by Nicholas Osler

Nicholas Ossler who wrote that book also wrote a wonderful book called Empires of the World of the No sorry Empires of the Word which is very dense. This guy has a very dense writing style but it's just full of delicious juicy tidbits about how language gets used and moves around. It's good for some some social linguistics absolutely stuff that you might want to incorporate into con worlds if you're one of those con lingers that also does con worlds.