The above book written in 1991 and updated in 1995 lists Cady's in six catagories. The first five cover John Cady (100), James Cady (2000), Daniel Cady (300), Nicholas Cady (400) and Joseph (5000) The six section list (6000) unattached members.. The update covers some corrections and updates. Since 1995, much more information has been found by researchers on familysearh.org, Ancestry.com and other search sites.
The book covers much of the information from Peer Orrin Allen, Daniel Cady Acton, and Scott Jorden, along with hundreds of researhers listed in the index. The book can be found in many Genealogy Libraries and occasionally on-line. I have a copy and I am working on an Excel speadsheet.
Written by Peer Orrin Allen in 1901 it lists many Cady's who loriginated in New England before 1840. After 1840 and outside of New England Cady's from Ireland and Germany started showing in Census records. Many just took the name Cady as to Anglosize their surname. In Ireland, Clans existed with surnames of Keady, Keedy, Keity and Cody. In Germany the surname most often changed was Cada. Some Cady and Kady's also arrived from England mostly outside of New England. The surname Caddy from Scotland developed seperately. Cade has some issues, it can be pronounced as Ca-id (French for a wine barrel) or Kai-dee a form of Cady. (Some Cady's choise this spelling.)
The surname Cady, was not listed in the Domesday Book (Census of 1085) but shows up on the Church Rolls of 1100. The origin of English names lists seven sources and Cady's nearly 60 possible origins fit into six. The most likely was assumed to be from Cad-ia a common first name in the ancient gaelic. The next most likely was based on a Ricardo de Cady born 1325, who was likely from a parish in Yorkshire referred to as Cady. Some research on the languages of ancient England point to the sound Kai-dee being the key and not the spelling. This likely means a Gaelic origin, not Irish Celtic, Welch, Scottish or Saxon.