Æt-berstan

According to the Old English Dictionary:

ic -berste, he -birsteþ, -byrst;

æt-berstan

p. -bærst, pl. -burston; pp. -borsten To break out or loose, to escape, get away; erumpere, evadere :-- Ða ælbærst him sum man evosit homo quidam, Gen. 14, 13. Ða fíf cyningas ætburstop fugerunt enim quinque reges, Jos. 10, 16. Ðæt he ðanon ætberste that he escape thence, L. C. E. 2 ; Th. i. 358, 25. æt-berstan