Why do the names of some Japanese prefectures contain 『しま』when, clearly, they are not island prefectures?


Why do the names of some Japanese prefectures contain 『しま』when, clearly, they
are not island prefectures?

For example, 広島 means "spacious/vast island," doesn't it? However, Hiroshima
is not an island... And there are more examples like this: 福 **島** 、徳 **島**
、and 鹿児 **島**.

I hope you can clear this up. Thank you!

