Urban Dictionary defines "Boo" as boyfriend of girlfriend; term of endearment.
Well, in her world of Fox News, Marty Balin concerts, computer class for seniors, and Sunday Mass, somehow Mama Hop didn't get the memo. It's a good thing she has Leanne around to keep her abreast of all of the current pop culture terminology.
Oh, that look of utter confusion on my mom's face is simply priceless; almost as priceless as my snort when Leanne first busted out the term in front of me. Where does she get this stuff?! I have no idea but I'm glad she does. It's 24/7 entertainment when Leanne is around.