Slavery by Another Name was created in 2008.
Slavery in one from or another has been going on for thousands of years. It is still going on.
Manumit
Depends on what slavery.Jewish slavery in Egypt.Jewish slavery in Germany.Indian slavery in the US.Indian slavery in Spanish countries.African slavery in the US.African slavery in Africa (enslaved by Portuguese and English).African slavery of Africans.Russian slavery of the poor.Chinese slavery of debters.You should clarify there were many movements in different locations. I guess we were all slaves at one point or another.
Abolitionists
The Cotton Gin created by Eli Whitney caused the spread of slavery.