Peats be with them!

Peace be with you. Shalom Aleichem (or Sholom aleichem) (Hebrew שלום עליכם shālôm ʻalêḵem; Yiddish שלום־עליכם şolem aleyxem) is a greeting in Hebrew, meaning "Peace be upon you". The appropriate response is "Aleichem shalom". http://en.wikipedia.org/wiki/Shalom_Aleichem

'Peace be with them' here refers to the dead oaks which have turned into peat. This natural cyclic process of death and renewal is central to the main themes in FW.

Peat is partially decayed vegetable matter and forms a large part of the soil in Ireland.