He looks to me to be from a race separate from the Hylians or the Sky people, one that uses magic, perhaps the interlopers that later became the Twili, maybe they were sort of demi-gods and he is one who has fallen from the path and has foul intentions. Or perhaps he is someone like Agahnim from A Link to the Past. He could be an agent of someone else or a higher power, or even someone from whom Ganondorf later learned his tricks. In the Link to the Past manga, Agahnim was actually a separate entity from Ganondorf, he was portrayed as someone who knew Link's Uncle and delved into magic -- he was used by Ganon from beyond the void, to break the seven seals. Like Agahnim, Ghirahim may want to seek access to the Golden Land or Sacred Realm where the Triforce resides... Ghira exists as a word in our world btw. In Arabic it can mean a kind of fierce self-respect, prestige and protective jealousy. In Sahih Bukhari - a Sunni Islamic book separate from the Quran - there are parables of sorts that talk of God / Allah's Ghira being greater than any mans. So what if Ghirahim is not actually your typical villain -- but a sort of fierce, arrogant protector of something? Maybe his people, or a secret power... I'd love it if Aonuma was trying to create another strange but sympathetic villain like Ganondorf in the Wind Waker. Even if he's not good, he certainly portrays an arrogance in the boss battle with link, and seems to prefer toying with him to killing him - so maybe there is something in the name.
The LTTP manga is here if anyone wants to read it:
http://zs.ffshrine.org/album/link-to-the-past/manga/chap01/l_zelda_comic_001.jpg -- just change 001 to 002 etc.