From under- +‎ breġdan.

• IPA^(key): /ˌun.derˈbrej.dɑn/

underbreġdan

1. to spread under
   • Wonders of the East

     Hī habbað miċle hēafda ⁊ ēaran swā fann. Ōþer ēare hī him on niht underbredað, ⁊ mid ōðran hȳ wrēoð him. Beoð þa ēaran swīðe lēohte ⁊ him beoð ān līchoman swā hwīte swā meolc. ⁊ ġif hī hwylcne mann on þām landum ġesēoð oþðe onġytað, þonne nimað hī heora ēaran on hand ⁊ feorriað hī ⁊ flēoð, swā hrǣdlīċe swā is wēn þætte hī flēogen.

     They have great heads and ears like fans. They spread one ear under themselves at night, and wrap themselves in the other. The ears are very light and their bodies are as white as milk. And if they see or perceive anyone in those lands, they take their ears in their hands and go far and flee, so quickly one might think that they flew.

• Joseph Bosworth; T. Northcote Toller (1898), “under-bregdan”, in An Anglo-Saxon Dictionary, second edition, Oxford: Oxford University Press.