The name 'McNicholl' means 'son of Nicholas,' and is most likely Gaelic in origin.
The 'Mc' part of McNicholl merely means 'son,' while 'Nicholl' is a derivation of 'Nicholas,' therefore 'son of Nicholas.' As for Nicholas itself, it is from the Greek name Nikolaos which meant "victory of the people," from the Greek nike, meaning "victory," and laos, "people". People named Nicholas are, knowingly or not, named after Saint Nicholas, the 4th-century bishop who, according to legend, saved the daughters of a poor man from lives of prostitution. He is the patron saint of children, sailors and merchants, as well as Greece and Russia.You May Be Related to Father Christmas!
St Nicholas formed the basis for the figure known as Santa Claus, the bringer of Christmas presents. Due to the renown of the saint, this name has been widely used in the Christian world. It has been common in England since the 12th century, though it became less popular after the Reformation.
Despite this, if McNicholl is your surname, your family roots are most likely in the Gaelic areas of Great Britain: Ireland, Scotland, the Isle of Man or possibly Wales. The clan MacNeacail originated in the Isle of Skye off the west coast of Scotland, so perhaps they hailed from that particular island. These days, you are as likely to meet a McNicholl in the USA or Canada than the UK, where the name is becoming less frequent. Here's one of the more famous McNicholls, Irish country singer John McNicholl, performing one of his songs: