The origin of the word is disputed. Some beliefs are that "mick" comes from the common "Mc" in many Irish names. McSorley, McNeil, McFlannagan, ect.
Others believe its related to the sound of a drunken hiccup. I was the captain *mick* of a ship *mick* for 3 years!!
Also, Mick is the word that "spick" came from.
Irish and Hispanics are both dominantly catholic. In the 1900's when Irish immigrants had pretty much been well established, but still hated by many Americans, was also the time when many Hispanic immigrants made their entry into America. They ended up sharing our churches, schools and neighborhoods due to the catholic faith and moral values we had in common. When early retard americans saw this, they bagan calling hispanics "spicks" (Like a spanish Mick).
Mick is also used between Irish friends and relatives in a playful and joking way.
Like "Joey, you stupid mick"
Also Mick is a word that Dutchman are afraid to use, cause they know that us Micks will tear em up. Like the guy "JESSIE" who posted earlier, they only say it on the web, or when we arent around.
"My cousin is one crazy mick"