"suaimhnigh sibhse!"

Subject to all the reservations implied in the rest of this thread (!):

First syllable : soov
Second syllable : nigg (short i, hard g) or nee , depending on dialect,
Third syllable : shiv (short i again)
Fourth syllable : sheh (as in "shell")

Stresses on first and third syllables.
Translation: "Calm yourselves!" (emphatic)

Regards