Before boiling it, the octopus' tentacles are dipped in and out of the boiling water three times, while being held by its head—this is meant to curl the tips of the tentacles. The tentacles are preferred over the head, which sometimes is discarded.
This passage describes a method of preparing octopus tentacles before cooking them. It emphasizes the importance of curling the tips and the use of boiling water as a key element.