IPA: //ˈsɛlfseɪm//
KK: /sɛlfseɪm/
Referring to the exact same person or thing that has been mentioned or is being discussed.
The selfsame book that I read last year is still on my shelf.
Selfsame → It is formed from "self" (from Old English "self", meaning oneself) and "same" (from Old English "same", meaning identical or the same). The word "selfsame" means exactly the same as oneself or identical to oneself.
Think of 'self' meaning oneself and 'same' meaning identical — together they remind you that 'selfsame' refers to something that is exactly the same as oneself.