Does anyone know of the first attested use of ‘sleep’ to refer to the dried rheum in the corner of one’s eyes after sleep? I’m having a hard time looking that up without getting a lot of false positives.

It’s come up on another forum that in English we have no specific word for it (besides crusties, eye boogers, etc) while other languages have some common used specific names such as ‘ramelas’ in Portuguese, ‘lagaña/legaña’ in Spanish, ‘çapak’ in Turkish, ‘muta’ in Tagolog, and ‘ettaorak/tötaorak’ in Marshallese. (I can’t vouch for any of that aside from the Marshallese).

The OED2 lists the sense “d. The effects or signs of sleep. Also spec., the solid substance found in the corners of the eyes and along the edges of the eyelids after sleep.
1864 LOWELL Fireside Trav. 103 A drowsy maid with the sleep scarce brushed out of her hair. 1905 in Eng. Dial. Dict. 1922 ‘R. WEST’ Judge I. iv. 195 Richard was sitting in front of the fire, rubbing the sleep out of his eyes. “ I’m doubtful the 1864 cite is what we’re talking about; sounds more like simple “bed head” to me.  It’s annoying that they don’t quote the actual definition from the 1905 dialect dictionary, but I’d bet it’s our quarry.  The 1922 clearly is.

The term favoured round here (Southern England) is sleepy dust.

1886 MRS. J. H. RIDDELL For Dick’s Sake i, Before London..has begun to rub the sleepy dust out of her great eyes.

FTR: no specific other word for it in Dutch either, other than ‘slaap’.

My mother used to call it “sand” after the sand-man nursery tale I suppose.  That is, “Waking up with sand in your eyes.” The sand man comes to sprinkle sand in the eyes of children to induce them to sleep.  Doesn’t make great sense, but there you have it.

North of England: sleep.

Based on the Beatles’ lyric “golden slumbers fill your eyes” I used to think that the British called those little crusty bits “slumbers”, but apparently that was a mistaken inference.

English surely has “sleep”, “sand”, “sleeper[s]”, etc. As well as “rheum”, “eye mucus”, etc. (more general).

In some languages, a compound which can be ‘translated’ “eye-shit” is used.

Here is a Japanese ‘idiom’ (16,000 claimed Google hits with this ‘spelling’ alone):

“目糞鼻糞を笑う” = “Mekuso hanakuso o warau”:

“me” = “eye”, “hana” = “nose”, “kuso” = “shit”, “warau” = “laugh”: “The eye-shit laughs at the nose-shit” or “The sleep [in the eye] ridicules the snot [in the nose]”. Comparable to “The pot calls the kettle black”.