The name Brain is a boy's name . Brain and discussed in our forums with posts like "Change one letter (5 names)".
From the experts:
Brain is not a name, it's a misspelling of the long-popular Brian. What's really astonishing is not that it made the Top 1000 at all but that it hung on there for 25 years, from 1965 through 1989, Brian's heyday. All we can say is: sad.