Question about a song - BINGO?

The Oxford English Dictionary has a 700-word note about this "o" under "-o". Boiled down, it says that there is a tendency in Modern English (16th century on) to tack an "o" on the end of words whimsically. It cites "kiddo", "cheerio", and "daddy-o". The "o" in the song is nothing new; sweet Molly Malone could tell you.