From Middle English panten, whence also English dialectal pank.
Possibly from Old French pantoyer, a byform or of Old French pantoisier ("to be breathless") (compare modern French panteler ("to gasp for breath")), of uncertain origin. Possibly from Vulgar Latin *pantasiō ("struggling for breath when having a nightmare"), from Ancient Greek φαντασιόω ("I am subject to hallucinations"), from φαντασία.