At almost every seaside village restaurant on Lesvos we saw octopus hanging from clotheslines to dry. Prior to drying, it undergoes a rigorous treatment which we were fortunate to observe one afternoon while sitting outside a taverna in Mytilini. An elderly fisherman, standing in water up to his knees in the harbor, laboriously tenderized octopus. Holding the octopus by a few tentacles he smashed it against a rock with great force over and over again...about 15 times. He then laid the octopus on the rock and took hold of a flat mallet, rather like the bottom of an ore, and hammered the octopus repeatedly. He then massaged the octopus against the rock for a few minutes. He repeated this with about a dozen octopus over the course of an hour. He then took his catch and headed off. Given the price of octopus, I hope he made a decent day's wage.
Here is the octopus salad I ordered in Sigri. It could have used a bit more pounding.