Learn more about Tarshish from the Easton’s Bible Dictionary

A Sanscrit or Aryan word, meaning "the sea coast." (1.) One of the "sons" of Javan (Gen. 10:4; 1 Chr. 1:7).
(2.) The name of a place which first comes into notice in the days of Solomon. The question as to the locality of Tarshish has given rise to not a little discussion. Some think there was a Tarshish in the East, on the Indian coast, seeing that "ships of Tarshish" sailed from Eziongeber, on the Red Sea (1 Kings 9:26; 22:48; 2 Chr. 9:21). Some, again, argue that Carthage was the place so named. There can be little doubt, however, that this is the name of a Phoenician port in Spain, between the two mouths of the Guadalquivir (the name given to the river by the Arabs, and meaning "the great wady" or water-course). It was founded by a Carthaginian colony, and was the farthest western harbour of Tyrian sailors. It was to this port Jonah's ship was about to sail from Joppa. It has well been styled "the Peru of Tyrian adventure;" it abounded in gold and silver mines.
It appears that this name also is used without reference to any locality. "Ships of Tarshish" is an expression sometimes denoting simply ships intended for a long voyage (Isa. 23:1, 14), ships of a large size (sea-going ships), whatever might be the port to which they sailed. Solomon's ships were so styled (1 Kings 10:22; 22:49).