Zzz is commonly used in comic books to indicate that someone is sleeping. It has also become a part of the idiom catch some Zs, which means to sleep.
Henry David Thoreau was the first writer to represent nonvocal sounds with the letter Z, but he was writing about the sound of crickets, not snoring. There are no firm rules about capitalizing zzz.
It’s unclear why zzz came to represent snoring. Henry David Thoreau was the first writer to represent nonvocal sounds with the letter Z, but he was writing about the sound of crickets, not snoring. There are no firm rules about capitalizing zzz.