[cauch]

I've a very dim memory of having heard about it years ago (more than a decades), from an article of Cory Doctorow, and in my mind, he was the one who came up with the idea (and chose the letters TK).

But I can be wrong (maybe it's not from Doctorow, maybe the article did not even claim the paternity of coming up with TK but it was me badly understanding it, ...)

[bobbiechen]

TK is a very standard term, see William Safire's usage in this 1996 NY Times article: https://www.nytimes.com/1996/10/06/magazine/of-hacks-and-tk....

[pm215]

Mmm. This Q&A -- https://www.chicagomanualofstyle.org/qanda/data/faq/topics/M... -- suggests it's been kicking around as printing and journalism jargon since at least the 1980s, and I would expect probably earlier.

[CommieBobDole]

Paywall-free link:

https://archive.is/Ipm3J