Kagawa Prefecture is known as the udon prefecture.
「〇〇と呼ばれている」は、意外とよく使う言い回しですよね。
上記に挙げた例文は、以下の「AはBと呼ばれている」という表現を使っています：
A is called B
A is known as B
ほかに「うどん県がないので、theが必要になることに注意しましょう。
ちなみに、オーストラリアのタスマニア州は、「The Apple Isle」（リンゴの島）と呼ばれていますよ。
It may seem strange but the alternative name for Kagawa prefecture is the "Udon prefecture"
Kagawa prefecture is informally known as the Udon prefecture because there are so many noodle restaurants there..
"Did you know that there are more than 700 udon restaurants in Kagawa prefcture?"
"No, I didn't. Why are there so many?"
'Well, Sanuki udon is a type of udon noodle and is the most famous local food of Kagawa Prefecture."
"Oh, I'd like to try some!"
"In fact, Kagawa prefecture is informally known as the Udon prefecture because there are so many noodle restaurants there and because of sanuki udon!"
例
"Did you know that there are more than 700 udon restaurants in Kagawa prefcture?"
香川県には700ものうどん屋があるのは知ってましたか？
"No, I didn't. Why are there so many?"
いいえ、知りませんでした。なんでそんなにあるの？
'Well, Sanuki udon is a type of udon noodle and is the most famous local food of Kagawa Prefecture."
讃岐うどんといって、香川でとても有名な食べ物なんだ。
"Oh, I'd like to try some!"
そうなんだ。食べてみたいなぁ。
"In fact, Kagawa prefecture is informally known as the Udon prefecture because there are so many noodle restaurants there and because of sanuki udon!"
実際香川はうどん屋さんが多いことからうどん県として知られているんだ。
Another name for Kagawa prefecture is "Udon prefecture".
An alternative name for Kagawa prefecture is "Udon prefecture".
Another name for Kagawa prefecture is "Udon prefecture".- This means you can use both names interchangeably and they mean the same.
An alternative name for Kagawa prefecture is "Udon prefecture".- An alternative name means another name for the same thing.
Another name for Kagawa prefecture is "Udon prefecture".
-これは名前をどちらにあてても、同じ意味になります。
An alternative name for Kagawa prefecture is "Udon prefecture".
- An alternative name とは、同じものを指す違う言い方、名前という意味です。
Kagawa is famous for UDON ( a thick wheat noodle) so its sometimes referred to as The Udon Prefecture
Kagawa is sometimes referred to as "The Udon Prefecture" because its their signature dish
A prefecture is a regional district in Japan;-D
(like a county in the UK)
Kagawa ken is a typical prefecture...but its FAMOUS FOR ITS EXCELLENT UDON;-)
So that is why it is sometimes called the Udeon Prefecture ...Simple really:-D
Nickname - a name given to a place, person or thing to replace their real name. People give each other nicknames when they are very friendly with each other.
Just like in the UK, certain areas or cities have a nickname, for example, Sheffield is often referred to as 'Steel City' because years ago there were many steel factories.
アメリカ合衆国 
イギリス 
南アフリカ 
オーストラリア 
