thumb is peuro

peuro = thumb (noun) (some things Google found for "peuro": an unusual to uncommon term; a rare last name; user names; part of a bad misspelling of Puerto Rico; several gaming character names; Iso-Peuro and Pieni-Peuro are lakes in Eastern Finland; similar Peura is the name of a town on the island of Sulawesi in Indonesia)

Word derivation for "thumb" :
Basque = erpuru, Finnish = peukalo
Miresua = peuro

Another new word for a body part. This word is one letter shorter than the shorter word, in this case the Basque word, which is OK under my rules.

The word thumb doesn't appear in Alice's Adventures in Wonderland. But it appears twice in Through the Looking-glass.

"That's just what I complain of," said Humpty Dumpty. "Your face is the same as everybody has -- the two eyes, so --" (marking their places in the air with this thumb) "nose in the middle, mouth under. It's always the same. Now if you had the two eyes on the same side of the nose, for instance -- or the mouth at the top -- that would be SOME help."