Michael Plant wrote:
> In the traditional Japanese tea ceremony an iron
> kettle is deployed over a charcoal fire. What is the
> Japanese word for this kettle?

"The Japanese Tea Ceremony" is, in fact, a collection of many different
versions of ritual. Most of the time, the water is heated in an iron
kettle over a fire. The lid is removed, and a bamboo dipper is used to
remove the hot water. This is called a kama.

Some versions of powdered tea ritual call for the use of an iron kettle
with a spout and a handle, thus eliminating the need for the dipper.
The kettle can be heated over a charcoal fire or an electric heater.
This is called a tetsubin, literally iron jug/bottle.

There is a book, in English, called _Tetsubin: A Japanese Waterkettle_
by P.L.W. Arts, Groningen [The Netherlands]: Geldermalsen Publications,
1987. This is a detailed academic work. Maybe you can find this by
inter-library loan. Paragon Book Gallery in Chicago might also have
occasional copies for sale.