Formally the word overlaps with both ostoir (‘soldier’) and oster² (‘inn-keeper’) – two rare and problematic words with entirely different etymologies. The glosses in TLL ii 68.65, which include the surprising deviant form hostilur (more likely, it appears, to be a form of osteler¹, i.e. ‘inn-keeper’) may indicate a certain level of confusion of the terms. There also seems to be some possible confusion between this word and ostriz¹ (see commentary). On the difficulties of the taxonomy of medieval bird-names, see David Trotter, ‘Tote manere d’oiseaus: Les noms d’oiseaux en Anglo-Normand’, Cahiers de Lexicologie 103 (2013), 125-43.