- A diminutive of the female given name Catherine and of its variant forms, also used as a formal given name in the 20th century.
- 1845 October – 1846 June, Ellis Bell [pseudonym; Emily Brontë], Wuthering Heights: A Novel, volume XVII, London: Thomas Cautley Newby, publisher, […], published December 1847, OCLC 156123328:
- It was named Catherine, but he never called it the name in full, as he had never called the first Catherine short, probably because Heathcliff had a habit of doing so. The little one was always Cathy, it formed to him a distinction from the mother, and yet, a connection with her; ( - - - )
- 2007 Kate Jacobs, The Friday Night Knitting Club, Hodder & Stoughton, →ISBN, page 124:
- 'Cathy sounds like the name of a truck-stop waitress,' she overheard her father-in-law tell Adam after they returned from their honeymoon. 'Tell her to call herself Cat and, for Christ's sake, get her to stop biting her lip all the time.'