What is happy as a lark?

The expression "happy as a lark" is a simile that describes someone who is very pleased and content. Larks are known for their cheerful and melodious songs, which they often sing as they soar high in the sky. Therefore, the phrase refers to one's happiness and light-heartedness that is comparable to the joyous singing of a lark. It originated in the 1700s, when a Scottish poet used the phrase in one of his poems, and has since become a commonly used idiom in the English language.