1 So up he rose, and thence amounted straight.

amounted > mounted, mounted up straight > straightway

2 Which when the carl beheld, and saw his guest

carl > villain, churl

3 Would safe depart, for all his subtle sleight,

for > despite subtle > crafty, sly sleight > trickery; knowledge; nimbleness of mind

4 He chose a halter from among the rest, 5 And with it hanged himself, unbid, unblessed.

unbid > not prayed for (cf. 101.30:7, 110.3:8)

6 But death he could not work himself thereby; 7 For thousand times he so himself had dressed,

dressed > disposed; put in that position; arrayed [with the halter]