hwæt - the MS hæt "hat" makes no sense in context. "hwæt" is the most generally accepted emendation. (see Blake 1961 for 'h' for 'hw') It forms the introduction to a clause forming a parallel object of "secgan" (Mitchell and Robinson p.159). Notice that several translations treat it anachronistically as if it were a relative pronoun but Bradley translates grammatically correctly. Emendation to "Þæt" has been argued for by Scragg. This would be a relative construction with the neuter gender agreeing with "swefn". (see Scragg 1968)