nox-nix
doesn't matter; no big deal; no biggie; no worries. A 19th century American southern corruption of the German phrase, "Machts nichst," meaning (lit.) "It makes nothing," or more idiomatically, "It doesn't matter."
"Hey Keri, I'm sorry I spelled your name wrong."
"You couldn't have known...nox-nix!"
"You couldn't have known...nox-nix!"