円
えん · en · JLPT N3 · noun
yen
💴⭕ en means round, and the yen was named after its round coins
円 is the simplified form of 圓, round or circle. In 1871 Japan named its new currency after round coins, so one sound covers both meanings. English writes it yen from an old romanisation; in Japanese it is plain en.
まる · maru · JLPT N3 · noun
circle
🪙 maru sounds like marble, and a marble is perfectly round
The same kanji is read en and means yen, Japan's currency, named after round coins. So 円 is both the circle and the coin. Read as maru it is usually written 円い (round); the more common maru kanji is 丸.