Jack Sprat (or Prat, or Spratt) was the 16th and 17th-century name for a dwarf. This rhyme was presumably written about a dwarf and his normal-sized wife.
However, there is a suggestion that there was a particular Jack Sprat – one Archdeacon Pratt and his wife Joan who lived in the 17th century – that this rhyme refers to.
Jack Sprat Lyrics
Jack Sprat could eat no fat,
His wife could eat no lean,
And so, between them both you see,
They licked the platter clean.