Celtic word for silver and etymology of the name Arganthonios

From: Michael Smith
Message: 33962
Date: 2004-09-02

Herodotus mentions a king in the Tartssus valley in Iberia named
Arganthonios, would his name come from the Celtic word for silver,
arganto, or could his name be derived from another Indo-European
root, maybe Lusitanian?

-Michael