The term tatara (kanji: 踏鞴) means "iron-smelting furnace" in English. It is written たたら in hiragana. It's pronounced roughly like "tah-tah-rah".
This refers specifically to the Japanese-style furnace used in the smelting of iron. Tatara iron manufacturing (たたら製鉄, tatara seitetsu) flourished in the Edo Period and declined with the introduction of Western methods near the end of that period.
Perhaps due to the difficulty of writing the second kanji, tatara is usually written in hiragana (たたら) in standard Japanese. The first kanji is generally used as the verb fumu (踏む), which means to step on or tread. The second kanji 鞴, by itself, is read fuigo and means bellows.