As it was the case of episode 6x17 Pot of Gold, there are several references to Ireland, its people and folklore:
Episode title: Slainte.
Slainte is Irish for 'health', used as a driking toast.
Declan Callahan: Luck of the Irish, huh?
'The luck of the Irish' is a catch phrase that is used to explain the good luck that makes a person of Irish descent beat some odds. Since Irish people have historically suffered many misfortunes, there seems to be some inexplicable and inherited form of good luck that makes things come out right for them.
Flack: You are stuck here with us while Declan lives the life of Riley down at his bar.
'The Life of Riley', a phrase meaning 'to live an easy and pleasant life' originated in the Irish/American community in the USA.
Mac: 8th to 12th. 34th to 59th. 59th and 12th. It's the corners (of Hell's Kitchen).
Mac: It's not even called Hell's Kitchen anymore.
Jo: Clinton does have a nicer ring to it.
'Hell's Kitchen', now referred to as 'Clinton', was a century-old hangout for Irish immigrants. The four semi-traditional boundaries or corners of Hell's Kitchen are the Hudson River west, Times Square east, Chelsea/Penn Station south, and the Garment District north.