Short answers, pulled from the story.
"Civil War" is the most common name for the conflict in the United States. It has been used by the overwhelming majority of reference books, scholarly journals, dictionaries, encyclopedias, and mass media since the early 20th century, and is the term used by the National Park Service.
The Confederate government officially referred to the conflict as the "War between the Confederate States of America and the United States of America". Confederate officials rejected the term "civil war" because it implied both sides were part of one country, which contradicted their claim to be a separate nation.
The term "War of Northern Aggression" was coined during the Jim Crow era of the 1950s by segregationists. They invented it to equate contemporary efforts to end racial segregation with 19th-century efforts to abolish slavery, framing both as illegitimate federal interference.
Frederick Douglass called the conflict "The Slaveholders' Rebellion" in a speech delivered on the 4th of July, 1862, in Himrod, New York. The name placed moral responsibility for the war directly on the slaveholding class.
No. Congress has never adopted an official name for the war. The United Daughters of the Confederacy lobbied Congress starting in 1913 to adopt "War Between the States", but that effort was unsuccessful.
Union forces typically named battles after nearby bodies of water or natural features, while Confederate forces used the name of the nearest town. This produced pairs like Antietam (Union) and Sharpsburg (Confederate), or First Bull Run (Union) and First Manassas (Confederate). Historian Shelby Foote attributed the split to the different ways urban Northerners and rural Southerners oriented themselves geographically.