My daughters have been tracing their O'Connor line and found that their great grandmother was named Mary A. Noon whose father was Michael Noon, born in Ireland in about 1835 according to the 1880 census.He immigrated to Maryland.He had a son named Michael born in 1861.
Mary A. Noon married Thomas P. O'Connor and had five children, only two of whom survived. Thomas and John. My daughters grandfather was Thomas Jerome O'Connor.
I will let them know the orgin of the Noon name you have posted.