What is "akitsushima"

Two ships of the Imperial Japanese Navy have been named Akitsushima, the ancient name for Japan:

• Japanese cruiser Akitsushima was a 2nd class protected cruiser, launched in 1892, and scrapped in 1927
• Japanese seaplane tender Akitsushima was a seaplane tender or carrier, which was completed in 1942 and sunk in 1944