From The Collaborative International Dictionary of English v.0.48:
Teache \Teache\ (t[=e]ch), n. [Cf. Amer. Sp. tacha, tacho.]
(Sugar Manuf.)
Any one of the series of boilers or evaporating pans in which
the cane juice is concentrated in making sugar; especially,
the last boiler of the series. --Ure.
[1913 Webster]
Note: The 1890 edition had the following etymology for
teache: [Cf. Ir. teaghaim, Gael. teasaich, to heat.].
Presumably a speculation which proved incorrect?