I don't believe there is.
The Mc is a bastardization of Mac, which means "son of", similar to the "-sen" or "-son" in scandanavian names: Mac Donald means "son of Donald".
The superscript 'c' is just a design thing, I believe. It looks kinda cool, especially in classic fonts (by which I n00bishly mean the fonts popular about when the superscript 'c' was popular; the 1920s-1950sish).
Properly, the Mc should be a Mac, and should have a space in between it and the following bit. Also, the Irish Mac's are probably Northern Irish, who are Scots who were resettled in Northern Ireland by (I believe) James I to spread protestantism through the Empire. [/history lesson]















