A squall is a "a sudden strong wind, often with heavy rain or snow". It can also mean to "to cry out loudly", although, it would most likely mean to former to match his personality.

The word "squall" has its roots scandinavian, sometime in the early 18th century. There are two words that the word is probably derived from either skval, Norwegian for "sudden rush of water", or skvala Sweedish for "to gush, pour down".

Since the term "squall" is of western origin, his name is written in katakana (romaji: sukōru). Moreover, it looks like the word has become part of Japanese terminology, much like many English words.

Squall name in relation to water and weather has a deeper significance. The name of his mother, Raine, and a variation of the word "rain", and his father, laguna, is Spanish for a "lagoon". It makes sense that Nomura would give Squall his name to futher the connection between the three. There is also seems to be a trend in characters designed by Nomura-- Cloud (Final Fantasy VII), Zack Fair (in relation to "fair weather"; Final Fantasy VII) Tidus (Okinawan for "sun"; Final Fantasy X), Sora (Japanese for "sky"; Kingdom Hearts ), and Lightning (code name; upcoming Final Fantasy XIII)-- all of these have a connection to the sky and weather.

His last name, Leonhart was Raine's last name. Since the game confirms the relation between Squall and Raine, he took his mother's maiden name. It's a mystery to why he would, since her tombstone in the final FMV reads "Raine Loire". "Leonhart" sounds very close to Lionheart, which is the last name of the famous British king from the Middle Ages (Richard Lion-hearted; Coeur de Lion). There's also the term lionhearted, which means one who is "very brave or courageous".