Stories We Like: A Guide to the Comma
c.1200, parlur, "window through which confessions were made," also "apartment in a monastery for conversations with outside persons;" from Old French parleor "courtroom, judgment hall, auditorium" (12c., Modern French parloir), from parler "to speak" (see parley (n.)).
Sense of "sitting room for private conversation" is late 14c.; that of "show room for a business" (e.g. ice cream parlor) first recorded 1884. As an adjective, "advocating radical views from a position of comfort," 1910.