Draco dormiens nunquam titillandus

[justcarol67]

No: HPFGUIDX 90418

Rincewind: 
The first word of Hogwarts motto is DRAGO not DRACO as in Malfoy 
DRAGO means Dragon. As far as I remember Draco was a Roman General, 
but It Does not mean Dragon.

Geoff:
Sorry to disagree. In the drawing in the UK editions, the first word 
of the motto has a "C" with a noticeable serif.
 
Draco is quite definitely Latin for dragon.

Carol:
It's also a constellation (Draco, the Dragon). Probably his mother
named him as part of the Black tradition of naming children after
celestial objects. Andromeda is a constellation; Sirius, Regulus, and
Bellatrix are stars. Not sure how that might tie in with the motto,
though. Maybe there's some connection with astrology or divination:
"Mars is red tonight."

BTW, the first Draco I'm aware of (really Drako, but I can't use Greek
letters here) was Greek, the Athenian tyrant from whom the adjective
Draconian (harsh) was derived. And, yes, his name meant "dragon," too. 

Carol, who can't find the motto in the American editions but does
remember a bit of high school Latin