was *probably* first used in Peter
Pan. But like the BtN entry says, there is some evidence that Wendy
was used before Peter
Pan. If that's true, then Wendy
's probably a diminutive of (most often) Gwendolen
, which means "white ring" (derived from the Welsh elements gwen "white, fair, blessed" and dolen "ring").
Wendy also could've come from other Gwen- names like Gwenyth, Gwenaelle, Gwenda, Gwenfrewi, Gwenllian, or even Guinevere.
So it all depends on whether you believe Wendy was first used in Peter Pan or not.