From Wikipedia:
“Tetsubin (鉄瓶) are Japanese cast-iron kettles with a pouring spout, a lid, and a handle crossing over the top, used for boiling and pouring hot water for drinking purposes, such as for making tea.”
and
“Outside Japan, a frequently seen variant is a cast-iron teapot that outwardly resembles a tetsubin. This type of teapot is glazed with enamel on the inside to make it more practical for tea brewing, though it can’t be used to heat water because that would break the enamel coating. In the west, these teapots are commonly referred to as tetsubin, although the Japanese call them “tetsu kyūsu” (鉄急須), or iron teapot, to make a distinction from the kettle. Cast-iron teapots often come with a tea strainer that fits inside.”
