piedra
/ˈpjedɾa/ · A2 · noun · f
rock
🪨 piedra = Peter: both from Greek petra, rock; petrify means turn to stone
From Latin petra, borrowed from Greek. The same root gives English petrify, petroleum (rock oil) and the name Peter (Pedro in Spanish). Latin short e became ie in Spanish, so petra turned into piedra, with t softening to d.