The phrase small potatoes denotes a person or thing considered petty, unimportant, insignificant or worthless. It is synonymous with small beer.
It originated in the USA in the early 19th century, but the English poet, critic and philosopher Samuel Taylor Coleridge (1772-1834) had used the image in a letter to the English poet Robert Southey (1774-1843), dated 17th July 1797, when evoking the English poet William Wordsworth (1770-1850):
(1895 edition by Ernest Hartley Coleridge)
Wordsworth is a very great man, the only man to whom at all times and in all modes of excellence I feel myself inferior, the only one, I mean, whom I have yet met with, for the London literati appear to me to be very much like little potatoes, that is, no great things, a compost of nullity and dullity.
The earliest instance of small potatoes that I have found is from The Boston Morning Post (Boston, Massachusetts) of 7th September 1832; the phrase, in quotation marks, was already well established, since its user punned on the literal and figurative meanings of small potatoes (Cape Cod is a peninsula in south-eastern Massachusetts):
The Onion Crop on Cape Cod, it is feared, will turn out rather “small potatoes” this year.
The phrase also appeared in the extended form small potatoes and few in a hill and variants. For instance, the following is from The Daily Pittsburgh Gazette (Pittsburgh, Pennsylvania) of 29th September 1835:
Vermont continues strong in the ranks of the opposition, having at the recent election returned three fourths of her members to the state legislature, either Antimasons or Whigs. The Van Buren forces are, in the language of an eastern editor, “small potatoes and few in a hill.”
On 11th September 1837, the Bangor Daily Whig & Courier (Bangor, Maine) published this paragraph:
THE LOCO-FOCO CAUCUS!
We understand that the loco-foco caucus on Saturday evening was a total failure that is, it was exceedingly small potatoes, and those very few in a hill. Paul R. Barker was unfortunate enough to receive the nomination for Representative. Mr. Barker is a clever fellow, and we are sorry that in his adherence to loco-focoism, he is “barking up the wrong tree!”