Izumi

Japanese: イヅミ - いづみ

…In some regions, instead of the entire Shichigosan festival, the three and seven days, or only the seven days, were celebrated. Once a child was old enough to crawl, a babysitter was placed in charge of the baby. Until then, however, there was a custom in various regions of raising the child in a straw basket called a Tsugura or Izumi, and placing the newborn baby in the basket on the third or seventh day. In addition, since there are many illnesses and ailments during infancy, such as night crying, colic, measles, and smallpox, various spells and superstitions are passed down in various regions. …

From [Tsugura]

...Rice straw nursery equipment. Also called Izumi or Ejiko. They are made in various sizes and are used to keep food warm in the winter.

*Some of the terminology that mentions "Izumi" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…地方によっては，七五三全部でなく，三つと七つ，あるいは七つだけを祝った。　子どもははい出すようになると子守をつけたが，それまではつぐらまたはイヅミなどというわら製の籠に入れて育て，3日目または7日目に生児をそこに入れる風習が各地にあった。また，幼児期には，夜泣き，疳（かん）の虫，麻疹（はしか），疱瘡など多くの病気や患いがあるため，各地には種々の呪法や俗信が伝えられている。…