Excavations for the widening of the N7 in 2004 unearthed evidence of early habitation, including a late Bronze Age/early Iron Age hill fort and three small ring barrows. Kill (Cill Corbáin) was reputedly the burial place of the nine Ui Faeláin kings (later to become the O’Byrnes) who were based at Naas (Nás na Ríogh), the last of whom, Cerball mac Muirecáin, was buried in 909. The 'motte' of John de Hereford's castle, probably dating from the 12th century, still survives on the outskirts of the village. A commandery for Knights Hospitallers was founded at Kilhill in the 13th century, by Maurice Fitzgerald, and chapters of the order were held here in 1326, 1332–34; it existed until the Reformation, when it was granted to John Alan.