Made-up words like “clisious” and “smanious” are easier to remember when they sound beautiful. Could the feel of a word shape how we learn languages, sell products and even how languages evolve?

Hash yer dothrae chek asshekh? This is how you ask someone how they are in Dothraki, one of the languages David Peterson invented for the phenomenally successful Game of Thrones series. It is an idiom ...