Definition & Meaning of "[whistle] in the wind"

What is the origin of the idiom "whistle in the wind" and when to use it?

The idiom "whistle in the wind" is believed to have originated in the United States in the early 20th century. The phrase is used to describe a situation where someone is speaking or making a statement that is unlikely to be heard or acknowledged, or where someone is making an effort that is unlikely to be successful or noticed.