A fender is a fire guard rail that sits in the front of a fire place within a building.
Actually it comes from de-fender which is similar to the way drawing room comes from withdraw-ing room.

By the way, HOLDEN the company has always called them Fenders. Every Holden parts manual refers to them as fenders. But being GM owned and influenced it's probably expected.
That said, a Tailgate is an End Gate and a Boot Lid a Deck Lid and of course a Bonnet is a Hood according to the same manuals.

Which brings me to:

Have you noticed in sport that defence has become "dee-fence" Another Americanism.