"It was so-called because it was the middle section of the trade route taken by many of the ships. The first section (the ‘Outward Passage’ ) was from Europe to Africa. Then came the Middle Passage, and the ‘Return Passage’ was the final journey from the Americas to Europe. The Middle Passage took the enslaved Africans away from their homeland."
http://discoveringbristol.org.uk/slavery/routes/from-africa-to-america/atlantic-crossing/middle-passage/
Outward Passage = Europe to Africa
Middle Passage = Africa to New World
Return Passage = New World to Europe
