"a stoat," especially in its white winter coat, late 12c., from Old French ermine (12c., Modern French hermine), used in reference to both the animal and the fur. Apparently the word is a convergence of Latin (mus) Armenius "Armenian (mouse)" -- ermines being abundant in Asia Minor -- and an unrelated Germanic word for "weasel" (represented by Old High German harmo "ermine, stoat, weasel," adj. harmin; Old Saxon harmo, Old English hearma "shrew," etc.) that happened to sound like it. OED splits the difference between competing theories. The fur, especially with the black of the tail inserted at regular intervals in the pure white of the winter coat, was used for the lining of official and ceremonial garments, in England especially judicial robes, hence figurative use from 18c. for "the judiciary." Related: Ermined.