A grimalkin is an old or evil-looking female cat

Cat

The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...

. The term stems from "grey" (the color) plus "malkin", an archaic term for a cat, derived from a hypocoristic

Hypocoristic

A hypocorism is a shorter form of a word or given name, for example, when used in more intimate situations as a nickname or term of endearment.- Derivation :Hypocorisms are often generated as:...

 form of the female name Maud. Scottish legend makes reference to the grimalkin as a faery cat which dwells in the highlands.

The term/name may first come from Beware the Cat (published 1570) by William Baldwin, who relates the story of Grimalkin's death. According to its editors, the story, and thus the name, originates with Baldwin. It is also spelled Grimmalkin or Grimolochin.

During the early modern period, the name grimalkin - and cats in general - became associated with the devil and witchcraft. Women tried as witches in the 16th, 17th and 18th centuries were often accused of having a familiar, frequently a grimalkin.

Notable examples

• "Gray-Malkin" was the witches' cat in the Shakespeare play Macbeth
  Macbeth
  The Tragedy of Macbeth is a play by William Shakespeare about a regicide and its aftermath. It is Shakespeare's shortest tragedy and is believed to have been written sometime between 1603 and 1607...
  
  

• In Tom Jones
  The History of Tom Jones, a Foundling
  The History of Tom Jones, a Foundling, often known simply as Tom Jones, is a comic novel by the English playwright and novelist Henry Fielding. First published on 28 February 1749, Tom Jones is among the earliest English prose works describable as a novel...
  
  , Henry Fielding relates a story from a 17th-century collection of fables in which Grimalkin is a cat whose owner falls passionately in love with her. He prays to Venus, who changes the cat into a woman. Lying in bed, however, she spots a mouse and leaps up after it, "Puss, even when she's a Madam, will be a mouser still."

• In Wuthering Heights
  Wuthering Heights
  Wuthering Heights is a novel by Emily Brontë published in 1847. It was her only novel and written between December 1845 and July 1846. It remained unpublished until July 1847 and was not printed until December after the success of her sister Charlotte Brontë's novel Jane Eyre...
  
  by Emily Brontë, Mr. Lockwood shares a set of two benches in the back kitchen of Healthcliff's manor with a Grimalkin described as a "brindled, grey cat, which crept from the ashes, and saluted me with a querulous mew."

• A cat that adopted Sham and Agba in King of the Wind
  King of the Wind
  King of the Wind is a novel by Marguerite Henry that won the Newbery Medal for excellence in American children's literature in 1949. It was made into a 1990 movie.-Plot summary:...
  
  , by Marguerite Henry