The Dictionary of Medieval Latin from British Sources ("DMLBS") is a valuable resource for word origins people. It was completed in 2013 after decades of work. I’d like to mention because I expect you’re probably unaware, in January 2016 it was put online for free. The address is http://logeion.uchicago.edu/index.html . The DMLBS dictionary cites its source-texts by abbreviated labels that are defined at http://www.dmlbs.ox.ac.uk/sites/default/files/DMLBS%20Bibliography.htm . It’s necessary to keep the definitions page at hand while using the dictionary, unless you’re just looking for a brief translation to English.
Another big, recent and valuable arrival online for free is the dictionary of medieval Greek Lexikon zur byzantinischen Gräzität ("LBG"), completed in year 2014, online at http://stephanus.tlg.uci.edu/lbg/ . It omits words that are defined in dictionaries of ancient Greek.
Another big and free medieval lexicon project, which has been online for, I think, about five years now, but is still a work in progress, is the dictionary of medieval Italian, Tesoro della Lingua Italiana delle Origini ("TLIO"), online at http://tlio.ovi.cnr.it/TLIO/ . It has gaps in its vocabulary. I feel it’s at about roughly two-thirds finished.
Another big and free project is the Spanish Corpus Diacrónico del Español ("CORDE"). It covers all periods but is particularly good with the later-medieval period. It is online at http://corpus.rae.es/cordenet.html . CORDE has a database of old Spanish texts. The texts are dated. You search for a word restricted to a time period and it gives you a one-line snippet, or a paragraph, for each instance of the word. Unlike the dictionaries I mentioned above, CORDE does not give you a definition of the word. In my use of CORDE I found a few of CORDE’s dates are bad, labelled older than they truly are. But on the whole I really like CORDE. It’s the way to do a medieval lexicon in the computer age: Put all texts in the database in searchable form and let the user do his own search.
AlWaraq.net—http://alwaraq.net/—does for medieval Arabic what CORDE does for medieval Spanish. AlWaraq.net doesn’t attach any dates to any of its texts. (More often than not, for people with experience with dating problems, reliable dating can be got from simply looking up the biography of the stated author in a biographical dictionary, though this is somewhat hazardous for people who are still greenhorns.)
For medieval Syriac and Aramaic, the Comprehensive Aramaic Lexicon ("CAL") is convenient for brief summaries, and it has links to several older dictionaries. It is at http://cal1.cn.huc.edu/ . CAL says it’s a work in progress, but from my experience I consider it finished in its essentials.
For medieval Netherlands Dutch, Instituut voor Nederlandse Lexicologie: Historische woordenboeken op internet, anno 2007, is the one. It is at http://gtb.inl.nl (I dislike its interface design in several different ways of disliking). Another free resource for Netherlands is the book Chronologisch woordenboek by Nicoline van der Sijs, which gives the date of first attestation of the words of the Netherlands language, downloadable as a PDF at http://dbnl.org/tekst/sijs002chro01_01/downloads.php . Some are terribly late, e.g. earliest for Dutch linnen = “linen” is 1236, earliest for Dutch wol = “wool” is 1240.
Other excellent lexicons of medieval languages are freely available online, but anyone who’s interested already knows them, probably.
I used the above dictionaries and other online sources to show that the medieval word “scarlet” came from Germanic (best attested in High German). The New English Dictionary on Historical Principles is badly mistaken when it says “scarlet” came from medieval Persian. The early records of scarlet in Italy and Latin Iberia explicitly say it is a cloth imported from Belgium and the north of France (and nowhere else), the word’s early records in High German and British Latin are among the earliest records in Europe.
