Old English þæc "roof, thatch, cover of a building," from Proto-Germanic *thakam (source also of Old Norse þak, Old Frisian thek, Swedish tak, Danish tag, Middle Dutch, Dutch dak "roof," Old High German dah "covering, cover," German Dach "roof"), from PIE root *(s)teg- "to cover."

Proto-Indo-European root meaning "to cover," especially with a roof. It forms all or part of: deck (n.) "covering over part of a ship;" deck (v.) "adorn;" deckle; detect; integument; protect; protection; stegosaurus; tegular; tegument; thatch; thug; tile; Tuileries.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit sthag- "cover, conceal, hide;" Greek stegein "to cover," stegos "a roof;" Latin tegere "to cover," tegula "tile;" Lithuanian stėgti "to roof;" Old Norse þekja, Old English þeccan "thatch;" Dutch dekken, German decken "to cover, put under roof;" Irish tuigiur "cover," tech "house;" Welsh toi "thatch, roof," ty "house."

late 14c., thecchen, from Old English þeccan "to cover, cover over, conceal," in late Old English specifically "cover the roof of a house," related to þæc "roof, thatching material," from Proto-Germanic *thakjan (source also of Old Saxon thekkian, Old Norse þekja, Old Frisian thekka, Middle Dutch decken, Dutch dekken, Old High German decchen, German decken "to cover"), from PIE root *(s)teg- "to cover."

"to adorn," 1560s, from be- + deck (v.). Related: Bedecked; bedecking.

in combinations, "having a (specified) number of decks," originally of vessels, 1795, from deck (n.). Later of stacked sandwiches.

"person regularly employed as a laborer on the deck of a vessel," 1839, American English, from deck (n.) in the nautical sense + hand (n.) "manual worker."

1835, of ships, "with two decks above the water line;" 1867, of street vehicles, "with two floors;" see double (adj.) + deck (n.).

1560s, from fore- + deck (n.).