"O Dei! Lava quod est sordium!" Which according to the Dresden Files novel I am reading means, "Cleanse what is unclean, O God."

So maybe I have a thing for latin battle cries ;)

Using alternate meanings for those words, it could also mean:
"Bathe as to the fact it is vulgar"
"Wash although it is niggardly"
"Soak since it is sordid"

And if you had instead said "O die" it would change to "Oh by day."

All considered Stephanus should have a new warcry now

SOAK SINCE IT IS SORTED!!! TAKE THAT ORGANIZATION!!! I THREW YOUR DAY PLANNER IN THE RIVER, KNAVE!