the.com/flashback

means A vivid, involuntary return of a past memory or scene into present awareness — or, in film and fiction, a deliberate narrative cut to an earlier time.

from A 20th-century compound of 'flash' (a sudden burst of light or instant) and 'back,' coined in the early days of cinema to describe cutting away to an earlier scene — the editing technique came first, naming the mental experience that followed; by mid-century 'flashback' had leapt off the screen and into psychology, describing memory that intrudes with the same jarring, uninvited speed as a film cut.