the "4" is there to signify 4WD.
QUADRIFOGLIO is a compound word made from QUADRA (either latin or greek origin) and FOGLIO. The QUADRA bit tells you that the FOGLIO has got four sides to it. Hence the literal translation: four-leaf clover.
Man, this badging business is a complicated one, isn't it?!
Wrinx, not to worry. Always a pleasure and an honour to help out! I just received Henry's email to tell me that he wasn't coming and that I was supposed to give you a copy of my Q4 workshop manual! Oops, one day too late. It's a shame really as I brought the manual with me in case I bumped into him but he didn't attend in the end. I'm sure we'll ahve another opportunity to meet sometime soon.