An Etymological Dictionary of the German Language/decken
decken, vb., ‘to cover, screen,’ from the equiv. ModHG. dęcken, OHG. dęcchan; the latter (with cch- from kj) from *þakjan, which was most likely the Goth. form; comp. AS. þęccan (obsolete in E.); OIc. þekja, ‘to cover.’ þakjan is a deriv. of the Aryan root teg (discussed under Dach), which appears with the same meaning in Lat. tegere, Gr. σ-τέγεω, Sans. sthagâmi. A str. vb. þekan corresponding to tego, στέγω, is is nowhere recorded within the Teut. group; the wk. vb. has assumed its function.