In his column Boilermaker recipe: drop the shot glass in the beer?, Unca Cec confesses that he does not know whether dropping a shot glass of whisky in beer was the original boilermaker, or is more properly termed a “Depth charge.”
Last night on a Law & Order re-run, Lennie referred to dropping the shot in the beer as a “Depth Charge.” Now, given Jerry Orbach’s life story in New York, I’m pretty sure he’s familiar with this kind of thing, and wouldn’t say something as Lennie that wasn’t true to life.
So, failing Unca Cec coming up with a more definitive answer, I’ll go with Lennie - the “Depth Charge” is dropping the shot glass into the whisky. Boilermaker is a shot with a beer chaser.
J.E.Lighter, in the Random House Historical Dictionary of American Slang, gives the first appearance in print of depth charge meaning a shot glass dropped into a glass of beer as 1956 in the book Don’t Go Near the Water. But it was referring to WWII.
The term Boilermaker appears earlier(during WWII and immediately afterward) indicating a whiskey and beer chaser.
My guess is they both evolved during the WWII period. Probably the original term was for the whiskey with beer chaser.
What about simply adding the whiskey to the beer without dropping in the glass?
My own upbringing suggests that this is a “boilermaker”. Dropping the glass in is a “depth charge”. A whiskey with a separate beer chaser is simply “a shot’n a beer”, as in “Pittsburgh is a shot’n a beer town.” (“imp’n arn” most likely).