LH I would guess that "take a boo" is more likely to come from the Cockney rhyming slang phrase which in full is "Take a butchers hook" that is "take a look" but as rhyming slang perversly, and to kep the meaning hidden from "outsiders, always left off the second term of the rhyme this was given as "take a butchers" at that! so it doesnt take much for the "butcher" to shorthen to "take a boo"