What is the Connection Between alienist and Alien?

Alienist looks and sounds like it should mean "someone who studies aliens," and in fact alienist and alien are related - both are ultimately derived from the Latin word alius, meaning "other." In the case of alienist, the etymological trail leads from Latin to French, where the adjective aliene ("insane") gave rise to the noun alieniste, referring to a doctor who treats the insane. Alienist first appeared in print in English in the 19th century. It was preceded by the other alius descendants, alien (14th century) and alienate (used as a verb since the early 16th century). Alienist is much rarer than psychiatrist these days, but at one time it was the preferred term.