Foul fa ye

I am familiar with the terms 'fair fa ye' and 'sonse fa ye', which are found in both Scots and Ulster-Scots and which wish someone well..  However I was unfamiliar with the phrase 'foul fa ye' until I came across it in the old Scots ballad Jamie Douglas.  It means to wish someone ill:

O foul fa ye, fause Blackwood
And aye an ill death may ye dee,
For ye was the first occasioner
Of parting my gude lord and me.