It's pronounced (shah-LAY-lee).
The Irish name for your basic war club, and this loverly word fits neatly into the song. What song? The one that's been playing in our brains for weeks now. Well, we put a little Irish/vintage spin on this groove, and it's printed on a grey heather cozy poly/cotton blend tee. Also... what's not to love about shillelaghs? Spread some Irish good will. Go ahead... sing it.