Where do CD8+ T cells originate?

CD8+ cells originate in the bone marrow. 

CD8+ cells are also called cytotoxic T lymphocytes or CTLs. They originate from lymphoid progenitor cells in the bone marrow. Immature T cells or thymocytes migrate from the bone marrow to the thymus where they undergo several DNA rearrangements resulting in a diversity of TCRs that are capable of recognizing antigens from foreign or intracellular pathogens.