spoilful > plundering, spoliatory Easterlings > (Presumably, Norwegians: cf. 210.41:3)
3 Long time in peace his realm established, 4 Yet oft annoyed with sundry bodragings
bodragings > hostile incursions, border-raids
5 Of neighbour Scots, and foreign scatterlings,
scatterlings > vagrants
6 With which the world did in those days abound: 7 Which to outbar, with painful pionings
outbar > keep out painful > arduous, toilsome pionings > excavations (to "pion" is to do the work of a pioneer in its original sense, i.e. digging trenches, preparing the way for the main army)
8 From sea to sea he heaped a mighty mound,
mound > embankment; hence: wall (see 411.36)
9 Which from Alcluith to Panwelt did that border bound.