There has been much umming and aahing; umpteen suggestions including Morwenna, Arvenn and (from someone who simply signs themselves "DCH" on their comment to the last entry on this subject) Ceefer. No, I have no idea what they meant either, but thanks for joining the conversation, DCH*.In the end, though, we plumped for one of the first ideas, so she's now officially "Tortue". For any non-French utterers, that's Français for "tortoise" because she's tortoiseshell coloured and is well and truly in her shell when it comes to socialising with us two legged folk.
If you're ever in Millbrooker Towers, you might get to meet her if you set up a hide and wait patiently for an hour or three.
*Mrs The Millbrooker has just interpreted for a Millbrooker with a very small brain that this translates as "Ceefer Cat". I get it now.