Bull hanky can be defined as an alternate
noun used in the place of word such as bull crap or bull s**t. It
came from a child that once referred to her snot as crap, and thus
came bull hanky.
"Do you know what Bill
said the other day,
Casey?" "No I don't, Jill." "He told me that the Einstein was an
idiot." "That's a bunch of bull hanky, Jill."