PARANYMPH.

I was looking at the Wikipedia article on Barcelona when a photo in the "Education" section caught my eye; it showed a large, attractive, light-filled room and was labeled "Paranymph of the UB." I am rarely completely thrown by an English word any more; I may want to look up the etymology or the details of the sense, but I can usually figure out the general idea, especially if it's a transparent classical formation, as this was: Greek παρα- 'para-' + νύμϕη 'bride.' But it clearly had nothing to do with brides. My first thought was vandalism (but who would vandalize a Wikipedia article by inserting the word "Paranymph"?); as a first step, I clicked on the photo to see the file name and discovered it was "Paranimf de la Universitat de Barcelona.jpg." This was the vital clue; I pulled down my Catalan Dictionary (a very odd book in that it has no indication of authorship) and discovered that paraninf (pronounced /pərə'nimf/) is Catalan for "main or central hall of ceremonies [university].' That solved the practical problem (and I changed the caption to read "Main hall of the University of Barcelona"), but left the problem of why the word had such an improbable meaning. Here the online Diccionari català was indispensable (note the different spelling of the word):

PARANIMF m.: cast. paraninfo.
1. En l'antiguitat, Padrí de noces, home que anava a cercar la núvia i l'acompanyava fins al nuvi.
2. El qui feia el discurs inaugural del curs en les universitats.
3. Sala d'actes principal en algunes universitats.
Etim.: del gr. παρανύμφιος, mat. sign.

So the meaning changed from the Ancient Greek 'friend of the bridegroom, best man' to 'one who makes the inaugural speech at a university course' (?) to 'main hall' (in which such a speech would be given). A lovely semantic transition, and one shared with Spanish (in which paraninfo means 'main hall, auditorium'); a quick check suggests it did not take place in any other Romance languages (paraninfo in Portuguese means "god-father, honor guest of wedding" according to my antiquated McKay's Modern dictionary, and in Italian it apparently means 'matchmaker'). The OED calls English paranymph "Now rare" and has the definitions "1. At a wedding: a bridesmaid or best man. Also fig." (last citation 1922 J. Joyce Ulysses ii. 375 "Juveniles amatory whom the odoriferous flambeaus of the paranymphs have escorted to the quadrupedal proscenium of connubial communion") and "2. An advocate; a spokesperson or orator who speaks on behalf of someone else. Now hist. and rare" (e.g., a1722 A. Pennecuik Wks. 368 "Yet for all that splendid show, you be But paranymphs of vice and luxury").