Any surname starting with "Nic" and ending with a Gaelic personal name is a woman's surname. Nic is a contraction of "nighean mhic" (Scottish) / "iníon mhic" (Irish), meaning "daughter of a son of," and is equivalent to Mac (son of) for girls and women.
This particular name is the feminine Gaelic form of MacDomhnall (MacDonald in English), though it's misspelled. The initial consonant in Domhnall should be lenited to produce NicDhomhnaill, and if it's Scottish, there should be a grave over the "o."
If your surname is short then it will probably have multiple source and saying the equivalent of "Surnameis 'Smith' therefore your family were once black smiths" is missing the fact that if your name came from a different country then that word means something different.
Maybe in the future they'll get more sophisticated.
Interesting that the three surnames with incorrect histories highlighted in the comments (so far) are all of Irish origin. Maybe the site is particularly poor with Irish surname origins?
http://www.irishtimes.com/ancestor/surname/index.cfm?fuseact...
Any way of telling how wrong I am?
Also, people gravitate towards naming their children after people (or just names) they like, whereas very few change their surname.
That actually sounds a bit high.
But, from Wikipedia, the ROK has about 20% of its population with the surname Kim/Gim/Ghim: https://en.wikipedia.org/wiki/File:Distribution_of_South_Kor...