The Hidden Meaning Behind Sirius' Name In Harry Potter
It won't come as any great surprise that J.K. Rowling put a lot of thought and significance into the names of her Harry Potter characters — you don't come up with "Rubeus Hagrid" by thumbing through the phone book. For the Black family, Rowling seemed especially focused on giving each character a name with some astronomical or mythological reference — the names of Black relatives Draco, Andromeda, and Bellatrix, for instance, are all stars or constellations (via HP Lexicon). Sirius is no exception to this, as he is named for the brightest star in the night sky, per Britannica.
The star Sirius, also known as Alpha Canis Majoris, is sometimes called the "Dog Star" because it's a prominent part of the constellation Canis Major, the "Greater Dog," according to EarthSky. This means that Sirius' name pointed to his secret ability to transform into a giant dog from the very beginning!
The mythology behind Sirius Black
There are other meanings hidden in the name "Sirius Black" as well, according to the invaluable Harry Potter resource MuggleNet. The word "Sirius" literally means "glowing" or "scorching," appropriate for both the brightest star in the sky and a man who escapes the darkness of his family (and his last name, straightforwardly meaning the absence of light). The Canis Major constellation is sometimes known as "Orion's dog" — in the night sky, the Canis Major constellation is found at Orion's "feet" (via EarthSky). As it happens, Sirius' father is named Orion, and by Sirius' account, he wasn't treated very well — he was such a disappointment to his parents that his name was burned off his family tree tapestry (via HP Lexicon).
The star Sirius was also once seen as a bad omen in the night sky, according to MuggleNet, much like the Grim that Sirius' dog form appears to be. There are other ominous portents in his name as well. The star he's named for may have originally been associated with the Egyptian god Osiris, the Egyptian god of life and death — fitting for a character who dies by falling through a mysterious veil between the two.