My favorite explanation (not verified) is that Blue Ivy is a human follow-up to Jay-Z's three "Blueprint" albums. Ivy or "IV" would be four in Roman numerals.
Mainly I just hope she's not named after Yankees blue.
In any case, it's hard to hate on Jay-Z's new musical tribute to his baby — if only because it's so heartfelt. He calls his daughter "a younger, smarter, faster me." (Sounds like someone I know.)
Here's to baby girls, whatever they're called.