Why is a deba thus named?

[Qapla']

Why is a deba known by that name? The word/phrase 出刃 doesn't seem very intuitively meaningful ("send out" + "blade"), and 出刃包丁 ("kitchen knife with its blade sent out"?) doesn't seem to make much sense.

 

[XooMG]

Wikipedia brings this up:
『堺鑑』には「その鍛冶、出歯の口もとなる故、人呼んで出歯庖丁と云えり」と記述されているが、これが普及や時間経過とともに「出刃」に変わっていったものと考えられる。

『本朝世事談綺』にも出歯庖丁について類似の記述がある。

 

[KenHash]

The common story is that 出刃comes from 出歯meaning "Buck toothed". And that the Sakai forger who first made it happened to be buck toothed. No idea if that's true or not.