mid-14c., panten, "breathe hard or rapidly," perhaps a shortening of Old French pantaisier "gasp, puff, pant, be out of breath, be in distress" (12c.), which is probably from Vulgar Latin *pantasiare "be oppressed with a nightmare, struggle for breathing during a nightmare," literally "to have visions," from Greek phantasioun "have or form images, subject to hallucinations," from phantasia "appearance, image, fantasy" (from PIE root *bha- (1) "to shine"). Related: Panted; panting.
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<a href="https://www.etymonline.com/word/panting">Etymology of panting by etymonline</a>
Harper, D. (n.d.). Etymology of panting. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/panting