You learn something new every day
In re-reading Tolkien's own lecture notes on Beowulf,
I found something I already knew: Wes hal
(short for wes þu hal
= May you be in health) is simply the polite greeting in Old English. And I also knew that that is the ultimate source of wassail.
What I did NOT know is that the typical Old English toast when proferring a tankard of ale was Beo þu bliðe
(= Be thou blithe). Which I think will make a fine response the next time Kevin raises a glass in my direction and starts spouting in Irish, Slainte agus saoghol agat!