There is a Welsh-Irish / Irish-Welsh on-line dictionary at:
I've only just begun to try it out. But a thought occured to me about
If you enter Welsh "tref" you get Irish "baile", which is well and
good and accurate.
But for someone already fluent in Irish, giving cognates as well could
speed up the acquistion of Welsh vocabulary, I think. (And the truth
is, if you already know Irish, Welsh is a piece of cake aside from
learning all the new words.) In this case of "tref", it could be
useful to see some of the Irish cognates in parentheses:
treabh = plow; occupy, inhabit
treabhachas = husbandry, farming; tribe, people
treabhlacht ( < treabh + lucht) = household, family
Does such a cognate dictionary already exist out there somewhere?