[a stone ]. An idol of the ancient Vandals settled in Lusace. It was a huge stone, draped, wearing a lion's skin over its shoulders, and designed to represent death. Mr. Lower says that the town of Flint in North Wales is named in honour of this stone deity, and gives Alwin Flint in Suffolk as another example. (Pat. Brit.) The Welsh call Flint Flint Teg-cingl (Flin's beautiful band or girdle).
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894