The etymology of G-man is a surprising one; its origin is not what most people suppose. You probably think that the word comes from “government man,” with the government in question being the US federal government. If so you are wrong.
The term originally appeared in Ireland in the early 20th century. The G is a reference to the G Division of the Dublin Metropolitan Police; at the time the G Division was the plainclothes detective division that investigated crimes and included a political section that investigated political crimes, especially in the aftermath of the 1916 Easter Rising and during the 1919-22 War of Independence.
The first recorded use of the term is in Margaret Skinnider’s 1917 autobiography Doing My Bit for Ireland about her role in the Easter Rising:
One morning I was informed there was a “G-man,” as we call government detectives, waiting down-stairs to see me.
James Joyce uses the term twice in Ulysses (1922). First on 8:420–21:
Jack Power could a tale unfold: father a G man.
And then on 12:270–71
The bloody old lunatic is gone round to Green street to look for a G. man.
Joyce also makes a reference to G Division in 15:131–32:
He was the eldest son of inspector Corley of the G division, lately deceased.
(Ulysses is set in 1904, but we cannot assume the term G-man was current at that early date. Joyce began writing the novel 1914, and it was first published in serial form between 1918–20.)
The first known American use of the term is in Fred D. Pasley’s 1930 biography Al Capone:
He offered a G man (Government agent) ten gran’ to forget it.1
So it seems that the term originated in Ireland as a term for a plainclothes detective and the G did not originally represent anything, it was simply an alphabetical designation of a particular division of the Dublin Metropolitan Police. Irish immigrants brought it to America, applied it to detectives on this side of the pond, and here the G was reinterpreted to mean government.2 (Although the Skinnider quotation hints that this reinterpretation may have been occurring in Ireland as well.)
There is commonly told tale that the coiner of the term was George “Machine Gun” Kelly, who first applied the term to federal agents during his 1933 arrest. But, as we have seen, the term was in use in the United States before this. This may possibly be the first time that federal agents became aware of their nickname, but it is far from the first use of the term.
2Dobbie, Elliott V. K., “Did ‘G-Man’ Come from Ireland?” American Speech, Vol. 32, No. 4 (Dec., 1957), pp. 306-307
Copyright 1997-2015, by David Wilton