Rún-cofa

According to the Old English Dictionary:

an;

rún-cofa

m. The chamber of secret counsel, the mind, breast :-- Hé mæg on his rúncofan rihtwísnesse findan on ferhþe fæste gehýdde (cf. ðonne fint hé ðær (on his gemynde) ða ryhtwísnesse gehýdde, Bt. 35, 1; Fox 156, 51), Met. 22, 59. run-cofa