This is a weird one!

[Dame Babs]

Just wondering why we call potatoes "spuds"?

[brachiopod]

I heard this on some programme recently. Simon Schama's 'History of Britain', perhaps?

Anyway, a 'spud'  was a small narrow type of spade. Since it was often used to dig potatoes, the tuber itself began to be called a spud.

[Don Quixote]

The best guess about the origin of the word "spud" traces it to a type of short-handled gardening spade known since about 1667 as a "spud", used for digging potatoes.  As a slang term for a potato, "spud" first appeared in print around 1845 in EJ Wakefield's Adventure in New Zealand, apparently in a discussion of local slang: "Pigs and potatoes were respectively represented by 'grunters' and 'spuds�."

[SimonMorton]

Granny Spud, not Granny Smith