Eschatos is the superlative of echō (to have/hold), meaning the last or extreme — the furthest extent, the final position. It gives us the English word 'eschatology' — the study of last things. Jesus says, 'The last [eschatos] will be first and the first will be last' (Matt 20:16). In Revelation 1:17, Christ declares, 'I am the First and the Last [eschatos].' Paul refers to himself as the least (eschatos) of the apostles (1 Cor 15:9) and the chief of sinners (1 Tim 1:15). The word appears in 'last days' (eschatais hēmerais), 'last hour' (eschatē hōra), and 'last enemy' (eschatos echthros).
Eschatos in its most theologically comprehensive use is Revelation 1:17's divine declaration: 'I am the First and the Last.' Christ brackets all of history — He was there at the beginning and will be there at the end. This is the Alpha-and-Omega of divine sovereignty over time. The 'last days' (eschatai hēmerai) are the age inaugurated by the resurrection — the New Testament consistently treats the present age as eschatological (Heb 1:2; Acts 2:17). Believers live in the 'last hour' (1 Jn 2:18) between the first and second comings. Every act of faithfulness is an act of eschatos theology — living as those for whom the end defines the beginning.