From Old Galician-Portuguese traado (13th century), from Late Latin taratrum (“auger”), attested by Isidore of Seville. Either from Paleo-Hispanic or from Gaulish, from Proto-Celtic *taratrom, from Proto-Indo-European *térh₁-tro-. Alternatively from Ancient Greek τέρετρον (téretron, “borer, gimlet”). Compare Galician trade, Spanish taladro.