Conventional CD4 and CD8 single positive T cell lineages constitute the main differentiation pathway in the thymus. In human thymus, a minor TCRαβ differentiation pathway diverges from the early double positive stage, consisting of CD10+ PD-1+ cells. These cells are phenotypically and functionally similar to murine agonist-selected intraepithelial T lymphocyte precursors (IELps) which home to the small intestine. Here, the progeny of the human agonist-selected IEL lineage was identified in antigen-inexperienced cord blood (CB) with a polyclonal T cell receptor (TCR) repertoire exhibiting a bias towards early TCR alpha chain rearrangements and elevated autoreactive indices. Single-cell RNA sequencing allowed further delineation of this unconventional lineage in CB. Trajectory analysis, along with TCR repertoire analysis, transcriptomics and proteomics, suggests a precursor-progeny relationship with the thymic IELps. The distinct, heterogeneous CB population can now be defined as CD3+ TCRαβ+ CD4- CCR7- CD26-. Besides recent thymic emigrants, this population also consists of newly identified effector clusters and previously described populations: the suppressive NK receptor expressing CD8+ Treg population, the KIR/NKG2A+ EOMES+ virtual memory population and the CD8αα+ T cell populations. The population shows a discriminating stable HELIOS expression and is exclusively able to downregulate CD8β expression, resulting in double negative T cells. The functional properties of this population suggest that the cells expand on inflammatory cues and exert cytotoxic and proinflammatory activity.