The language is difficult but worth prising apart. And the poet uses the very grammar to come to his assistance, intricate complicated clausal sentences for example when Gawain is trying to avoid the Lady's advances. Middle English is in some ways like a computer program that you love to hate - but oh how much you learn and what things you can do when you understand it.
I have slightly adapted the above to fit the tweet but it comes from the end of Gawain's journey when he hears the axe with which he is about to be beheaded being sharpened by the Green Knight. It is an eerie passage.
In full, it runs as follows:
þene herde he of þat hy3e hil in a harde roche
2200bi3onde þe broke in a bonk a wonder breme noyse
2201quat hit clatered in þe clyff as hit cleue schulde
2202as one vpon a gryndelston hade grounden a syþe
2203what hit wharred and whette as water at a mulne
2204what hit rusched and ronge rawþe to here.
2205þenne bi godde quoþ gawayn þat here at I trowe
2206is ryched at þe reuerence me renk to mete
Gawain thinks he is about to die:
A very strange noise came from the rock in the high hill over the burn clattering against the cliff like it might break them apart, like a scythe on a grindstone whetting, and it whirred like water through the mill wheel, rushed and rung and evil to hear. 'My God,' said Gawain, 'that mortal is getting the gear ready that will kill me when we meet.
If you get the chance to go to Danebridge in the Peak District, you can find your own way to the Green Chapel. I would recommend it. Who knows what you will find there...
More on Gawain here: http://books.google.com/books?id=utiWYyWMEl4C.
Once you start reading this poem, you may find you never stop.