French: à la mode (fashionable), au fait [with] (fully informed about something), au revoir (goodbye), badinage (banter), beau monde (fashionable society), décolletage (low-cut neckline on women’s clothing), double entendre (something which can be interpreted in two ways, one of them dirty), femme fatale (seductive woman with a bad effect on men), né, née (male and female respectively, born, as put on forms for a woman’s maiden name), protégé (protégée if female; a person helped by a patron); raison d’être (reason for living); recherché (refined, known only to connoisseurs); risqué (almost indecent); R.S.V.P. (répondez s’il vous plaît, please reply).
German: There are assimilated war-related terms which are not given an initial capital letter, including flak (an acronym for anti-aircraft fire) and blitzkrieg (lightning war). U-boat retains its capital letter, as do Sturm und Drang (Storm and Stress). Other words keeping the capital letter include Doppelgänger (double in the sense of a look-alike), Übermensch (superman) and Zeitgeist (spirit of the age). Musical terms include Lieder (songs).
Greek: hoi polloi (the common people)