Shamus was an American slang term for a police officer or private detective, possibly derived from the Irish name "Shamus". It was occasionally used in the novels of Raymond Chandler as a somewhat derogatory name for the detective Philip Marlowe.

Shamus is also the name of a chatacter in John le Carre's novel The Naive and Sentimental Lover

The phrase was also used in the film The Big Lebowski in succession to several other synonyms for detective.

Detective: I'm like you! A brother shamus!

The Dude: You mean, like, an Irish Monk?

Detective: What the f*** you talkin' about?

Shamus is a very Irish name. S"h"amus is the original name not Seamus. If you interview Irish men names Shamus you would see thats the right spelling. Its a popular name in Ireland and much better than Adnan or Kenan. Those names are just rediculous.