> DIL under 'airdech' refers to a legal phrase 'rath tar airdig'
> "precise meaning unclear" and gives a number of examples (one to
> do with contracts even). Anything on that one?
It is still obscure. It is used of clientship contracts. It appears to
refer to cases in which one's lord secures additional services by paying
an additional grant ('rath') over and above one's normal 'cup full'. My
guess is that it may have something to do with the fact that clientship
contracts were sealed at an ale-feast.