What's a futcheon?

[Thomas Paikeday]

I think this qualifies as a "good question"!

I am surprised no one apparently asked it for 37 years, Allen Walker Read
assumed it didn't need an explanation, and it happens to occur in a locus
classicus.

If I may speculate, I think it is a blend of  "futchel" and "escutcheon" and
means - my imagination fails here. I'm sure someone on the list will come up
with a better explanation.