On Guani is a phrase that is a way of saying that someone is telling the truth. Similar to other phrases such as "I swear to
God." Other common uses are "On my
mom," "On my grandma," "On my grandpa," "On
gang," etc...
Person 1: I whipped out of that parking lot so
fast, spinning the
wheel, I 'bout flipped the damn
car over. Then the police started following me, and I had to run away.
Person 2: Really?
Person 1: On Guani