My four-year old niece telling me about her new pet gerbil: “I like to hold him but don’t squeeze him hard. Then he would die. Then he would have X’s on his eyes.”
I knew she must have got that idea from cartoons, but it got me to wondering where that originated. Animated cartoons or older print comics, or even earlier art? Any ideas?
I’ve seen it in comics dating back to the 30s (?). No earlier than the 1890s I think, and starting in the assembly-line illustration of newspaper cartoons.
It caught on. It’s an easy shorthand to distinguish dead (X) from sleeping (-)
I’ve seen X’s used for unconscience characters, but they were knocked out, not just asleep.
They probably had stars and little birds around their head too. 
Everybody got to elevate from the norm - Rush
Could it have anything to do with the tradition of putting coins over the dead’s eyes? Using “X” as a monetary increment, of course.
“Teaching without words and work without doing are understood by very few.”
-Tao Te Ching
It’s used for dead-drunk, too, which raises the possibility that the iconic “XX” on whisky barrels and bottles may have a connection.
John W. Kennedy
“Compact is becoming contract; man only earns and pays.”
– Charles Williams
Search engines are better now than they were in 1999, but I’m not having much luck finding a decent answer to this. I don’t care why X’s are used, but who started it and when?
I have seen somewhere that this was originated by Peter Arno.
I have a hunch: it’s a crude depiction of “tache noir,” which is the black or brown line that forms across a dead person’s eyeballs (from where the white is exposed to the air.)
It can look x-like when it crosses the cornea.
I had actually been planning to ask this very question at some point in the future!
In comics / cartoons, “Xs” are often used to denote that a character is dead, or if not dead, then knocked out (at least that they have been hit hard on the head, even if they may still be conscious). Would be great to know who came up with this device and whether there’s some meaning behind it.
I would like to suggest this possibility: could the X have originated as a simplified way of illustrating eyes that have been shut very tightly, so that the centers of the eyelids are pressed tightly to each other and the lines of the “Xs” depict wrinkles around the edges of the eyelids? I got this impression from a book that my kindergarten teacher read to us many years ago. The story went something like this: a boy wanted to be a duck and tried to act like one. One night, one of his books from the bookshelf above his bed fell on his head and knocked him out, causing him to have a dream that he had become a duck, and to find out that being one was not all it was cracked up to be. At first, I was confused by the illustration where the book falls on his head, as his shut eyes were drawn as three crossed lines each (so not Xs - that is, two crossed lines) rather than as one line each. When I looked at the illustration again, it occurred to me that this was simply meant to indicate that the eyes had been shut very tightly, resulting in wrinkles on each side.
Similarly, if you look at this illustration from another book from my childhood, “The Cat Came Back”, when the cat is hit on the head by a brick, its eyes are shown to look not like Xs, but like 6-pointed asterisks. Again, could this suggest that the eyes have closed very tightly, causing the eyelids to wrinkle?
There is this guy (in a drunken stupour, not dead)
whose eyes are X’d yet wide open, suggesting a deliberate joke on a trope where X = eyes shut
The eyes are the windows to the soul.
An “X” has long been short-hand for something being “crossed out”: nullified or negated.
At death…the ultimate nullification…the “soul windows” are representing the soul’s permanent expulsion from the mortal coil.
I’ve long “known” that it is because morticians used to sew eyes shut, so the x represents two big stitches. No?
I came here to say that (including the “windows to the soul” quote). It always seemed obvious to me.