An article from 1934 in Time about Mr Oscar Ulysses Zerk.

Mr Zerk's US patent 1,619,454 for a lubricant receiving nipple was filed on 05 July 1923 and granted on 01 March 1927. I think it's probable that the public came to call a Zerk lubricant receiving nipple, just a plain old zerk. If you search the US PTO site for patents with the inventor Zerk you find a lot more lubricant-related inventions.

Ceci n'est pas un seing.