Which way? Who? No, we're not paraphrasing lines from the old Abbott and Costello routine "Who's on First?" We're referring to the etymology of qua, a term that comes to us from Latin. It can be translated as "which way" or "as," and it is a derivative of the Latin qui, meaning "who." Qua has been serving English in the capacity of a preposition since the 17th century. It's a learned but handy little word that led one 20th-century usage writer to comment: "Qua is sometimes thought affected or pretentious, but it does convey meaning economically."