Green’s Dictionary of Slang

cheater n.

[fig. uses of SE]

1. [1910s+] an adulterer.

2. [1920s] (US) a glass eye.

3. [1920s] (US) an act of adultery.

4. [1940s] a condom.

5. [1940s+] anything that makes a task simpler, provides safety, gives one advantage, etc.

6. see cheator n.