yerrr is a saying that new york city people say when they see a friend or cousin or sibling, uncle and ect
me;yerrrrrr
friend; yerrrrrr hi bruv
new yorker for "lets goooo" kind of like cheering "yes!"
mostly a Brooklyn/bronx thing
New Yorker #1: "We outside"
New Yorker #2 #3 #4 in unison: "Yerrrrrrr"