A hesitant suggestion:  'tiar' in the Irish custom of directions is 'back,
behind, and 'after'.  Taobh thiar de X = behind X.  Could what you are
looking for be '(and) after that hourney'?


David Stifter wrote:

>>> conid tíar dind fecht sin fúair a bás tria ét Ailella.
>> tíar = in the west
>> dind fecht sin = from that expedition
> The combination of "west of, in the west" and "journey, expedition; 
> occasion, time" is unusual.

It struck me as odd, too.  I immediately thought of Modern Irish expressions
such as "taobh thiar de = behind" which combine "tíar / thiar" and "de".
But that doesn't fit, and I don't think that "tíar de" can have a temporal