The akaname (垢嘗 literally, "dirt licker") is a monster from Toriyama Sekien's Gazu hyakki yagyō, probably based on a creature called aka-neburi from the Kokon Hyaku Monogatari Hyōban (古今百物語評判), a collection of stories from the Edo period.
Sekien did not include explanations along with the drawings, but today the akaname is often described as a being that appears in messy bathrooms to lick away dirt and dust with a poisonous saliva.
The story is sometimes used to scare children into keeping the bathroom clean. This explanation seems to have originated in a 1920s anthology of Yōkai art.
In classical yōkai depictions, we find children with claws on their feet and squat heads wandering around the baths sticking out their long tongues.
These depictions do not have any kind of explanation, it is possible, therefore, only to infer their meaning, but in the Edo period Kwaidan book Kokon Hyakumonogatari Hyōban, there are mentions about yōkai called akaneburi (neburi means "to lick") and it is inferred that akaname is a representation of this akaneburi.
According to the book Kokon Hyakumonogatari Hyōban, the akaneburi is a monster that lives in old toilets and hides in dilapidated properties.
In those days it was believed that since fish are born in water and lice are born in dirt, and at the same time fish feed on water and lice feed on dirt,
then there was a belief that these creatures feed on the material that generated them, the akaneburi is that creature that is generated from the air full of dust and dirt, so it feeds by eating dust and dirt.
In yōkai literature from the Shōwa, Heisei, and beyond periods, akaname and akaneburi have been interpreted as above.
These interpretations state that the 'akaname is a yōkai that lives in old, decaying bathhouses and buildings and sneaks in at night while people are sleeping to lick the dirt and grime attached to baths and bathtubs, using its long tongue.
This creature does nothing but lick dirt, and was considered very creepy to encounter, for these reasons people worked very hard to make sure the bathrooms were clean so the akaname would not come in.
Since no one has ever seen an akaname its true appearance is not known, but aka reminds people of the color red (aka in Japanese), they are also called "red faces" or are thought to be entirely red.
In addition, aka (meaning "dirtiness") also has ties to the idea of "impurity" such as "depravity", "sin" or "worldly desires" and other things that are not necessary, leading to the theory that it was not simply a story about keeping bathrooms clean, but also about preventing impurities from hiding in one's self.