ermines

Attested in this form (with s) since at least 1562, in Legh's Accedens of Armorie, which defines it ("Sable poudred with Argent, … Ermines is his proper name") and contrasts it with both ermine and erminois. Related to ermine, but the derivation is unclear; the OED suggests "possibly [from] OF. herminès, pl. of herminet" (a supposed diminutive of hermine); modern French calls the fur contre-hermine.
The Fifteenth Century Book of Arms (c. 1460) uses ermyne in a way that sometimes contrasts with ermyn (“ermine”) ("John Garther beryth of ix pecys ermyñ and ermyne"); The Ancestor says the image of that blazon "shows the furs as those usually called at this date erminees (or erminee) and ermine—erminees being ermine with the colour reversed. It is evident that the maker of this roll, whose blazonry is sadly to seek, was uncertain by what name to call the ermine with the black field and white tails. On a later page of this MS. [fo. 59] we find ermine described as ermyñ and its reverse as ermyne)." The Middle English Dictionary defines that use of ermyne as "having the fur ermines, consisting of black with white spots (instead of black on white)", although they derive it from, and it appears to be, erminé ("ermined") instead, hence the Fifteenth Century Book also records a bend "sabyll ermyne" and a lion sable with "ermyne appon the sabyll".