I was curious about this line in one of the letters cited:

>Gutapercha ring making is all the go now by the men and some of them are making really beautiful ones.

So wikipediaed gutapercha, which turns out to be a tree. The same name is used for a latex made from the tree. This material made undersea cables possible in the early days.

But I was curious: why rings? Well, it might have something to do with the caning of Charles Sumner in 1856. Brooks, a pro-slavery U.S. representative beat Sumner, an abolitionist representative, nearly to death on the Senate floor with a gutapercha cane. Brooks' colleagues then wore necklaces with rings made from the shattered cane. So that letter might've come from a Confederate soldier.

So how did the 'due date' meaning arise? Was it related in some way to the prison line?

Edit: according to wiktionary, in the 20th century it was used in the printing industry for a line on the bed of a press beyond which text wouldn't print, then by analogy as a time limit after which a newspaper story wouldn't make it into the paper. It's not clear if this sense was inspired by the Civil War prison dead lines, or made up independently.

I would not be surprised if there was a totally separate etymology for deadline in the chronological sense. Publishing and journalism have plenty of related terms, e.g. a "kill fee" for an article that is submitted but not printed. Always seemed to me that the meaning and etymology was self-evident: a piece submitted after the line on the calendar or schedule would be "dead," i.e. killed and not published.

> This concludes your exercise in pretending to not waste time while actually avoiding your deadline. Now: get back to work.

I suppose this could serve as the unspoken signature line in most communiques. Thanks MW

This apparent etymology is fascinating, but the article left me disappointed in failing to actually connect the spatial dead-line to the chronological deadline.

There’s a hint that it started to become used metaphorically toward the end of the 19th century, but without any examples of early usage or even speculation as to how a spatial metaphor became a chronological metaphor, the origins of the modern usage remain a mystery.