An Etymological Dictionary of the German Language/Annotated/Deich
Deich, masculine, ‘dike’; Middle High German tîch, masculine; since the High German word would, according to phonetic laws, begin with t, we must suppose that it has been influenced, like Dampf perhaps, by Low German; compare Low German dîk, Dutch dijk, Anglo-Saxon dîc, English dike. Respecting their identity with High German Teich and English dike (‘a ditch’), see Teich.