Europeans began to practice the lucrative slave trade, which took place for four centuries between the African continent and the American continent. The slave trade brought about changes in African society, because the increase or decrease of internal slavery (in Africa) was related to the greater or lesser external demand (for America). Therefore, the greater the need for slaves in America, the greater the number of enslaved people in Africa. Thus, slave trade became a profitable business. For this reason, African traders began to search for more people to enslave.
Mother tounge is basically just the language from your culture.
Explanation:
When somebody says something is in their "mother tounge" it means it is in their native language. For example, "The Sioux man recited a poem in his mother tounge, his face alight with passion."