ptarmigan: [16] Ptarmigan was borrowed from Scottish Gaelic tarmachan, a diminutive form of tarmach ‘ptarmigan’. There is no etymological justification for the spelling pt-. It was foisted on the word in the late 17th century in the erroneous belief that it had some connection with Greek pterón ‘wing’ (source of English pterodactyl). [ptarmigan etymology, ptarmigan origin, 英语词源]
bird of the grouse family, 1590s, from Gaelic tarmachan, of unknown origin. The pt- spelling (1680s) is a mistaken Greek construction (perhaps based on pteron "wing").