Different websites give conflicting opinions regarding this surname. What is the origin of Griffin when used as a surname?
Griffin is often incorrectly described as being simply of Welsh origin. For example:
In reality if we look at phonebook data, it is clear that Griffin is primarily of Irish origin.
Dublin Ireland, 216/1,271,000 = 0.02% Clare Ireland, 87/117,196 = 0.07% Kerry Ireland, 201/145,502 = 0.1% Cardiff Wales, 22/341,000 = 0.006% Bangor Gwynedd Wales 2/18,808 = 0.01% Wrexham Wales 2/65,692 = 0.003% Birmingham England 40/1,074,000 = 0.004% Leeds England 22/474,632 = 0.004% Southampton England 4/253,651 = 0.001% Manchester England 16/514,417 = 0.003%
I used the Eir phone book for Ireland and the BT phone book for Wales and England. I've divided the number of entries in the phonebook by the local population when arriving at the local percentage with the surname.
Additionally, note that many of Wales' and England's Griffins are of Irish extraction, due to large levels of migration from Ireland to Britain. Of course, the surname Griffin may well have unique sources in both Wales and England. For example, Griffin is probably an alternative spelling of Griffiths in some instances.
Here is a map showing the distribution of Griffin per capita for Britain and Ireland:
The surname Griffin has numerous sources in Ireland. For example, in Kerry the name comes from the Gaelic surname Ó Grifín while in Clare it comes from Ó Gríofa.
See also: Griffin Surname Maps
According to the Dictionary of British Surnames:
Griffin F/N A diminutive of Griffith; or a nickname for a fierce person ME griffin (gryphon, a heraldic beast); Irish: Anglicized form of Gaelic O' [descendant of) Griobhtha ('gryphon'). Gtiffing is a scarce scattered variant.
Personally this is my go to book for Surname origins.
The usual origin is a patronymic based on a diminutive of the Middle Welsh name Gruffudd, either transmitted directly from the Welsh, or via Breton immigrants who came over to England with William the Conqueror. (See Reaney & Wilson: A Dictionary of English Surnames, s.n. Griffin; for example Osbertus filius Griffini 1153-68.)
The same Welsh name is the source of the Irish surnames Grífin and Ó Grífin. (See Woulfe, Irish Names and Surnames s.n. Grífin: https://www.libraryireland.com/names/g/grifin.php.) However, there are other Irish surnames that end up looking and sounding like "Griffin" in English, and some of them are more likely derived from an Irish given name Gríobhtha, which Woulfe derives from words meaning "gryphon-like, fierce warrior" (https://www.libraryireland.com/names/og/o-griobhtha.php).
Either way, however, the surname Griffin originates as a patronymic or relationship-based byname, naming the father or other ancestor of the bearer.