Why is our nations capital named Washington D.C., and what does District of Columbia stand for?

The term "District of Columbia" is derived from an old poetic name for the United States, Columbia, which has fallen out of common use since the early 20th century.

Federal districts are subdivisions of a federal system of government. Often, these districts are not one of the countries' component subdivisions, and should not be confused with them, but are rather separate entities under the direct control of the federal government. The seat of the federal government is often located in a Federal District, so that no single individual component can exercise undue influence over federal affairs.