The name Flash is a boy's name of English origin. Flash and is often added to lists like Badass Baby Names and discussed in our forums with posts like "Picky Parents BNG".
From the experts:
Flash Gordon makes this a superhero name, but Flash might just appeal to modern parents looking for one of the new active boys' names, ala Ace and Breaker and Ranger. We'd recommend something more pulled-together as a proper name with Flash as a nickname or middle name.