Washington State's original name was Columbia. It was changed to avoid confusion with the District of Columbia.
In what was clearly the smartest move in history until Netflix’s ill-fated decision to divide into two companies to remedy its price hike, the state of Columbia was changed to Washington so that people wouldn’t confuse it with Washington, DC. Washington is officially named as such after George Washington, the first president of the United States. It’s also the only state to be named after a president.
Today, to avoid mixing it up with Washington, DC, it’s often called Washington State, while Washington, DC, is often just called DC. Originally, it was named Columbia, after the Columbia river, but it was renamed not long after. It's not really clear how the name change would accomplish a distinction. Maybe they should have named it after another president.