We have only just begun to cover Gawain in my Medieval Lit class, but I am sure that I like it better than almost everything we have read so far, at least as far as poetic art is concerned. Marie de France may win, story-wise, but… Anyway, as I read, I am making a list of words for which I would like the meaning, the specific medieval usage or the etymology. I often do this, and filled a whole pocket mini-spiral with words before I made it one third of the way through Burton’s Anatomy of Melancholy (which I still want to go back, re-start, and this time finish), but Gawain is not quite as bad, at least in this modern translation by Borroff. Still, I will never actually get around to looking up all the words I have gathered on random slips of paper unless I get them off of random slips of paper and out into the open where people who notice that I haven’t added definitions and the like can prod me like the child that I am. Here is, therefore, the list. It will grow as I read, so if you are interested, stay tuned.

girt
In Gawain, it seems to be used as a form of the verb “to gird” to mean to encircle with a belt or belt-like item, either literally, in order to hold up or contain items of clothing, or figuratively, to prepare or arm oneself.
crupper
Interestingly enough, this word widened or morphed in meaning from a saddle strap that was fastened to a horse’s tail to keep the saddle from sliding toward the horse’s head, to a horse’s rump, to any rump (especially that of a human), to the rump-cut of meat from an animal. It came from the Teutonic word “croup” which meant just that: rump.
gentle
At the time of Gawain, and for a while after, this word referred to a person’s being of good birth or status - much closer to our modern “gentleman” than gentle’s current non-synonymous twin. Gentle and gentile are both derived from a Latin word meaning “of a good family”.
broidered
I was already pretty sure that this meant the same thing as embroidered, but was unsure about which came first. It looks like broider may have, but not by much. The big difference seems to be that broider(ed) has a narrow meaning encompassing only needlework, embroider(ed) has come to have figurative uses as well.
foretop
In this translation of Gawain, this refers to the shock of hair that grows out from between the ears of an animal (in this case a horse).
dock
adown
dint
appurtenance
helm
hauberk
ell
chary
ween
gisarme
by Gog
recreant
roisterous
doughty
minstrelsy
handsels
welkin
wroth
Michaelmas
greaves
cuisses
thick-thewed
couters
caparison
baldric
cavil

Just for the record, the information given about these words is from the the holy, holy OED, but spat into this blog only after having been well-chewed by my brain.