"Easy there!" (4,2)
(Other definitions for cool it that I've seen before include "Modern injunction to calm down" , "Modern expression for calm down, or reduce heat" , "Here's what to do before opening champagne" , "Don't get so excited'" , "Relax" .)
(Other definitions for whoa that I've seen before include "halt" , "Order (horse) to stop" , "horsy expression?" , "Opposite of "Giddy-up!"" , "Hold your horses!" .)