'Growltigress' is the name of one of my cats, my wife calls me 'Big Tigs' amongst other things (the cat is nicknamed 'Little Tigs' or 'Geroff' yew bastard') because I am bouncy, pouncy, flouncy, trouncy, fun, fun, fun, fun, fun (I think). Hence 'Growltigga' and like Dogscoff, no-one else is sad enough to use it.
"Growltigga" was also in TS Eliots' 'Book of Practical Cats' as the swashbuckling pirate bravo cat who was eventually made to walk the plank by some siamese.
Kind of fits with my roguish, piratical but fun-loving persona