"Seasoning" was something which took place prior to the sale of slaves in America. Some who were sent directly to North America by passed seasoning though those sent to South America always underwent seasoning.
In the West Indies, particularly Jamaica, the slaves would be acclimated to life as slaves. Seasoning was meant to develop the behaviors expected of slaves including learning the "patios" language that allowed communication between new slaves, existing slaves and slave masters. Many slaves did not live through the seasoning process.
The "seasoning" process also included cleaning, debugging and taring that covered wounds and sores. After sale, the slaves would be branded with the owner's mark and given new names. Families, if intact, were broken up with men, women, and children seasoned and sold separately.
"Seasoning" slaves benefited the slave traders because "seasoned" slaves brought in more money than slaves brought directly from Africa.