Historical Meaning (OED)
Historically, inclusion meant the act or state of including: bringing someone or something within a defined group, boundary, category, or whole.
Derived from Latin includere (“to shut in” or “enclose”), the original meaning was neutral and operational: something was either included or excluded according to a stated boundary. The distinctly social sense—deliberately including people regardless of race, gender, age, or disability—emerged later in the 20th century.