Private Eyes

Photo of a shammes in Poland in 1926, shown knocking on the 

shutters of a home summoning men to a shule (synagogue) service

From OzTorah
http://www.oztorah.com/2008/02/shammes-shamus-ask-the-rabbi/

A shammes (or shammas) is an official acting as the beadle, sexton, and caretaker of a synagogue (from the Hebrew shammash, “to serve”). What my dictionary says about shamus is “US slang: a police or private detective, probably from shammes, influenced by Irish Seamas, James”.

The origins of the shammes go back to Talmudic times. In those days his title was chazan, which did not denote a cantor but a synagogue overseer. He was a versatile individual with responsibility for the synagogue building, the conduct of services, the allocation of seats, the supervision (and sometimes teaching) of children, and even acting as court official and sheriff.

In time the offices of chazan and shammes were separated. The chazan chanted the services; the shammes became the general factotum whose duties ran from community administration to announcing lost property and proclaiming the results of law suits...

I am interested in word origins, and "shamus" is one of those.
To be precise, I am interested in goofy etymologies - explanations of word origins that are daft, yet keep turning up in print.

The derivation of "shamus" from the Celtic name Seamas, or James, makes no sense whatever, unless we postulate some alternate history and universe wherein St. James the Greater and St. James the Lesser were not only Apostles of Jesus, but had been recruited by Jesus after he had left the Sea of Galilee - having landed Simon Peter and the sons of Zebedee - and had gone to Capernaum to the No.1 Greater or Lesser Detective Agency to run a background check on the new Galileans.
There he found the James boys.

However, if you look closely at the photo at the top of the shammes, he is standing near enough to the window to eavesdrop and peek inside. This reminds us immediately of  Jake Gittes in Chinatown saying talking about having to do "divorce" work; i.e., catching some poor cheater in flagrante delicto and taking the snapshots for the aggrieved wife.

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