Kizen Sasaki noted that perhaps they are the spirits of children who were crushed to death and buried at the home.[15] In the Tōhoku region, infanticide was called usugoro (臼殺, or "mortar kill"), and it is said that children who were killed this way to reduce the number of mouths to feed would be killed by being crushed by a stone mortar. Afterwards, burying them in the dirt floor room (doma) or in the kitchen was a custom. It is said that the spirits of such children would, on rainy days, walk around outer edges, shaking and frightening the guests, which is said to be seen to resemble deeds similar to that of a zashiki-warashi.[10] The aforementioned notabariko and usu-tsuki warashi are seen to be lower ranking among the zashiki-warashi, and the former would peek out from the inner dirt floor (doma) room and crawl around while the latter would use a mortar to make a sound. Due to such acts,[12] it is sometimes suggested that these kinds of zashiki-warashi have a relation to the fact that the location where the infanticide happened is in the dirt floor (doma) room or underneath a mortar.[3]