the "cn" in the tower's name came from the "canadian national" railway, the railway company that built the tower. in 1995, the railway sold the tower to the canada lands company (clc). local residents wanted to keep the name "cn tower", though, so the abbreviation is now a shortened form of canada's national tower instead of the original canadian national tower. neither of these names are commonly used, though; the tower is usually called the cn tower.