Final answer:
The term 'involuntary servitude' in the Thirteenth Amendment refers to all forms of compulsory labor that are coerced, and it was abolished alongside slavery, except as a punishment for a duly convicted crime. Congress is empowered to enforce this prohibition with appropriate legislation.
Step-by-step explanation:
Justice Brown did not directly state the function of the term involuntary servitude in the Thirteenth Amendment. However, according to historical context, the term 'involuntary servitude' in the Thirteenth Amendment was designed to expand the scope of the amendment beyond just the formal institution of slavery.
In the amendment, 'involuntary servitude' signifies any form of compulsory labor or service coerced through force, threats, or other forms of coercion, and it was constitutionally abolished alongside slavery. The only exception allowed is for servitude as a punishment for a crime, where the individual has been duly convicted in a court of law. Additionally, Section Two of the Thirteenth Amendment grants Congress the power to enforce the abolition of both slavery and involuntary servitude through appropriate legislation.