The "naginata" was developed from an earlier weapon type of the later 1st millennium AD, the "hoko yari". It is difficult to tell when the "naginata" itself first appeared; though often claimed as being invented by the "sōhei" during the Nara period, physical evidence of their existence dates only from the mid-Kamakura period, and earlier literary sources are ambiguous. The earliest clear references to "naginata" date from 1146 in the late Heian period, with one suggesting that the weapon had been recently developed. Earlier 10th through 12th century sources refer to "long swords" that while a common medieval term or orthography for "naginata", could also simply be referring to conventional swords; one source describes a "naginata" being drawn with the verb "nuku", commonly associated with swords, rather than "hazusu", the verb otherwise used in medieval texts for unsheathing "naginata".