selfsame

Etymology

PIE word *swé From Middle English self sam, self same, selve same (“the very same, selfsame”) [and other forms], from self (“that specific (person mentioned), herself, himself, itself, themselves”, pronoun) (from Old English self, ultimately from Proto-Indo-European *swé (“self”)) + sam, same (“(adjective) equal, identical; unchanging; referred to earlier, abovenamed, aforementioned; (adverb) again, repeatedly”) (from Old Norse samr (“same; agreeing, of one mind”), ultimately probably from Proto-Indo-European *sem- (“one, together”)). The English word is analysable as self + same. cognates * Danish selvsamme (“identical, selfsame”) * Old High German selbsama (“identical, selfsame”)

adj

1. Chiefly preceded by the: precisely the same; the very same; the same not only in being similar but in being identical.
   [T]hrough my police issue 200 × 6000 macroscopic laser-prism binoculars I could see he was the same guy who had just bopped the doorman in the head. […] But you can imagine my surprise when I angled said state-of-the-art bins to the street, watched the long black car as it rolled up and saw the self-same guy step out of it. 1992, Robert Rankin, chapter 12, in The Suburban Book of the Dead: Armageddon III: The Remake, London: Bloomsbury Publishing, page 131

noun

1. (archaic) Chiefly preceded by the: precisely the same person or thing.
   So ſtrictly is the Specific Nature preſerv'd in the Individuals of the ſame kind, vvho all equally partake of it, and are ſo very reſembling and uniform in it, that they ſeem but as ſo many Self-ſames, ſo many Reproductions of one thing, like the Image of the ſame Face repeated by a Multiplying Glaſs. Thus for Inſtance, in Men, there is the ſame common Human Nature in all of them vvithout Intenſion or Remiſſion, the ſame Intellectual Frame, the ſame thinking Principle, the ſame rational Faculties, the ſame Radical Deſires and Inclinations, the ſame Natural Affections, the ſame Springs of Paſſion, &c. 1701, John Norris, “The Reality of the Distinction Justifi’d, by Shewing that This is Not the Only State of Things, but that They Have an Ideal as Well as a Natural State”, in An Essay towards the Theory of the Ideal or Intelligible World.[…], part I, London: […] [Samuel] Manship,[…]; and W[illiam] Hawes,[…], →OCLC, page 50