 The full etymology is unknown . The oldest known usage of the word is in the 794 text Shin <unk> <unk> <unk> <unk> . Other old sources include <unk> <unk> ( <unk> – <unk> ) and <unk> <unk> ( c . <unk> ) . These oldest sources are written in Man <unk> which clearly identifies the historical spelling as <unk> . Following several <unk> <unk> changes , this becomes kitsune . 
