Argon

Argon was the fourth child of Fingolfin, the High King of the Ñoldor in Beleriand in Middle-earth.

History
Argon was probably born in Tirion and his mother was Anairë, and his brothers were Fingon, and Turgon. He had an older sister, Aredhel. Argon set foot on Middle-earth with his father and brothers, but he was killed during the Battle of Lammoth.

Etymology
Arakáno thus never received a true Sindarin name, but Argon was later devised for him in the records. It is recorded that this later became a popular name under the Eldar. His Quenya name was Arakáno ("High Commander"), named so partially for his character.

Argon is also the name of a chemical element.

Other versions of the legendarium
Argon does not appear in the published The Silmarillion at all, as he only came to light in very late writings by Tolkien.