Fóre-costian

According to the Old English Dictionary:

-costigan;

fóre-costian

p. ode; pp. od [ = for-costian] To profane, pollute; profānāre :-- Gyf rihtwísnys mín hí forecostigaþ si justĭtias meas profānāvĕrint, Ps. Spl. C. 88, 31. fore-costian