What is "halirrhothius"

Halirrhothius was the son of Poseidon and Euryte (or Bathycleia) in Greek mythology. When Halirrhothius raped Alcippe, Ares's daughter by Aglaulus, Ares killed him. Ares was tried in a court made up of his fellow gods. The trial was held on a hill adjacent to the Acropolis of Athens, known as the Areopagus. Ares was acquitted.

In another version of the myth, Halirrhothius was sent by his father to cut down the olive that had grown out of the spear of Athena. As he raised his axe, it fell out of his hand and mortally wounded him. The olive was called "fatal" from that circumstance.