The Pogues started as Pogue Mahone, but changed their name when someone spread out what it meant in Irish.
Just confirm what my Irish colleages have said, and buff it up a bit.
*Tóin *means arse, buttocks or backside. It means ass only in the rude USAian sense - which derives from the same root as arse. A donkey has a tóin but is called an asal
Póg means kiss, both verb and noun.
Mo means my. *Mo *changes the sound of the following consonant, which is signified by adding h after the consonant. So, the word tóin sounds like “thone”. After mo, the initial t becomes th, making it thóin which sounds like “hone”.
So, “póg mo thón” means “kiss my ass” in the normal derogatory sense, with no donkeys involved. It’s pronounced roughly “pogue muh hone”.
I remember reading a short story years ago by an American author, who named the Irish female character Pogue Mahone. I don’t know if he had been conned by some Irish person, or was playing a trick on his US readers.
I accidentally a waitress at a pub, is this bad?
Only if you her tóin.
Be be be be be 
In fairness, if it’s a Dublin waitress and especially one in a traditional pub, anyone would want to. It’s just human nature.
Another easy phrase - “Hoof hearted? Ice melted.”
Yes to both. She really likes the atmosphere. She talked to a few, and was not at all discouraged. She said a landlady promised to hold her job for a few years until she returned. 
We should note that ‘ass’ for ‘donkey’ is used much more in Irish English than it is in English English. ‘Ass’ for ‘buttocks’ does not belong in English English at all, nor indeed in Irish English, however the wide spread of American TV makes people here more aware of it than formerly.
Study of the Irish language remains compulsory in all schools in the Irish Republic, a fact which did not endear the language to many who were compelled to learn it against their inclinations. The way in which it was taught, often rather heavy-handed, did not foster a liking for it - the memoirs of Peig Sayers, an illiterate peasant women who, in the 1930s, dictated her memories of rural poverty and backwardness to her son, who wrote them down and got them published, featured prominently. Despite the large amounts of public funds poured into nourishing the language since 1922, the number of speakers who are truly fluent continues to decline.
So the t-shirt is a bilingual visual pun?
Trilingual, really, counting American English into the mix.