Hechler forcing is described on page 278, Jech.
Does anyone know when Hechler forcing was first used in a publication?
The citation is given on page 283 of Jech (at least, in the 3rd Millenium edition); it is to Hechler's paper "On the existence of certain cofinal subsets of $^\omega\omega$," in the collection "Axiomatic Set Theory II" (see http://www.ams.org/books/pspum/013.2/9987/pspum9987.pdf), which is the only paper by Hechler in Jech's bibliography. It is somewhat difficult to read, but I think that we call "Hechler forcing" is a simplified version of the forcing introduced on page 159 of that paper; it seems reasonable to assume that this is its first instance.
(An historical note: Jech cites Hechler's paper as "," which is the date the collection "Axiomatic Set Theory II" was published; but that collection is the proceedings of a symposium held in 1967.)