It's true that in Georgian / Regency England (well, Great Britain) most people were still beholden to the "classics" in terms of personal names: John, Mary, Henry, Catherine... This was especially true of those in the upper echelons of society. Names from mythology, or Shakespeare, started trending with the emerging bourgeoisie in the middle of the nineteenth century (around your recorded first appearance of Daphne in Great Britain), and this is theorized to have derived from art they patronized: books, paintings, plays, operas, etc. Parents heard or read character names, became fond, and decided to actually use them as a way to be unique (essentially, nineteenth century "fandom" names).
This was seen by the upper classes as rather
gauche. I remember reading Jane Austen's
Emma and how it was implied (through Emma's eyes) the moment the sisters Augusta and Selina were introduced that they were nouveau riche and not up to Emma's standards. Such an impression began with their very names - and that was early in the nineteenth century!
So yes, Daphne Bridgerton is anachronistic in regards to her name. But those of us who enjoy these romances forgive authors like Quinn for writing Daphnes, Evangelines, Lavinias, etc. before their time - because the alternative is every other lady being named Mary (with some Catherine/Katherines, Eleanors, and Biblical classics scattered throughout).
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