←
Old English þrǣl (inherited)
←
Old English þrǣġan (cognate)
←
Middle English thral (inherited)
←
Middle English threl (mention)
←
Proto-Indo-European *trāgʰ- (derived)
←
Old Norse þræll (derived)
←
Old Norse þræla (cognate)
→
English thirl (mention)
→
Old English þrag (cognate)