According to to the French-language Wiktionary,
pochin is an Old French word with the probable meaning of ‘little bag’, a diminutive of
poche ‘bag’. Your French dictionary will probably tell you that today
poche means ‘pocket’ or ‘pouch’, but here in the southwest of France, a shopkeeper may ask you if you want a
poche to take your purchases away in.
That word poche is Germanic in origin: French got it from Frankish, and its English etymon still survives in the phrase a pig in a poke.
But, in English, pochin seems only ever to have been a surname only, not a word with a definite meaning.
I can’t find it in any English-language reference, other than Wright and Halliwell-Phillips, which give ‘hedgehog’. I even tried the University of Michigan’s Middle English dictionary, and the University of Aberystwyth's Anglo-Norman dictionary, and drew blanks there too.
With the one exception of Wiktionnaire's Old French citation, taken from Godefroy, all of the Google hits on pochin are for names (well, up to the first 6 pages, anyway).
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