Baro (BA-dough) is a word that comes from the greek term that means pressure or weight (as in barometer). In Spanish "weight" is "peso", and "peso" is the currency in Mexico. Therefore, baro is used as a substitute of "peso" in expressions like:
Préstame dos mil baros, ¿no?
Can I borrow two thousand pesos?
Baro can also be used as a synomym of dinero (money) as a reference to cash or wealth:
Don Ramón: Me gustaría invitar a Doña Florinda a cenar, pero no traigo baro.
Chavo: Doña Florinda es una arribista buscando un marido de baro.
Don Ramon: I would love to take Doña Florinda out for dinner but I'm broke
Chavo: She's an arriviste looking for a wealthy husband.
Baro is also used to refer to something cheap and therefore of questionable quality in the expression "de a baro", meaning "worth one peso" or approximately 8 cents of a dollar:
Beto: ¿Qué te regalaron tus suegros en navidad?
Enrique: Un pinche suéter de a baro.
Beto: What did your in-laws give you for Christmas?
Enrique: A stupid and cheap cardigan.
Enrique: A stupid and cheap cardigan.
In the image below is one baro coin from the 1960s.