Under-creópan

According to the Old English Dictionary:

under-creópan

to enter surreptitiously; surrepere :-- Ða wæs ðæs wítegan cnapa mid gítsunge undercropen avarice crept into the heart of the prophet's servant, Homl. Th. i. 400, 16. Ðæt ne feónd ús undercreópe (but the Latin is subripiat), Hymn. Surt. 12, 28. under-creopan