it occurs to me now that people may not get this joke. when lighting the candles during hanukkah, you are to light one candle and then use that candle to light the others. the candle that lights the others is called a "shammes" which means "helper", derived from hebrew "shamash". a similar sounding word, "shamus" which is the title here, meant police officer, before eventually meaning private investigator. it is theorized that these two words are related, though it's also possible that it may derive from the irish name "Seamus" because of the history of Irish police force.