Wendy wasn't an original name created by JM Barrie. There are quite a few Wendys in censuses taken before Peter Pan came out (and they're not the names of young girls but of fully grown women so it had been around for at least 30 years before Peter Pan. I believe it is a diminutive form of Gwendoline.

There have been very few true Anglo Saxon names that have come down the ages mainly the ones already noted, Godgifu being a favourite of mine (IIR the correct spelling) meaning gift from God.