Recorded as Keady and sometimes Keedy, but originally with the Mac or O' prefix, this is an Irish surname. It has it is said, two separate origins. The first claims that it was anciently spelt Mac Ceadaigh, from cead meaning "one hundred". Precisely why anybody or a clan should be called "One hundred" seems to be something of a mystery, and one not explained by any of the authorities on Irish surnames. The name seems today to be most recorded in County Galway, but to have originated in Queens County (now County Leix). However it is rare there now, and rarer anywhere with a prefix. There is another branch of Keady in County Cork, but it is claimed, that there is no relationship between them. It seems that the Cork nameholders were originally O' Meiceidigh, which spelling became corrupted to Mac Ceadaigh. Well there you are! All we can add is that the original Cork spelling as Meiceidigh whether it be with O' or Mac, often interchangeable with Irish surnames, looks suspiciously like the Mac Ceadaigh. The surname was well recorded in County Longford and County Leix in the census of Ireland in 1659, and at that time does not seem to have been recorded in County Cork. The first recording may be that of Teag O' Keady in County Mayo in 1635 in Staffords Inquisition.