deck (v.2) Look up deck at Dictionary.com
"knock down," c. 1953, probably from deck (n.) on the notion of laying someone out on the deck. Related: Decked; decking.
deck (n.) Look up deck at Dictionary.com
"covering over part of a ship," mid-15c., from a nautical use of Middle Dutch dec, decke "roof, covering," from Proto-Germanic *thakam (source also of thatch (n.)), from PIE root *(s)teg- "to cover."

Sense extended early in English from "covering" to "platform of a ship." Meaning "pack of cards" is from 1590s, perhaps because they were stacked like decks of a ship. Deck chair (1884) so called because they were used on ocean liners. Tape deck (1949) is in reference to the flat surface of old reel-to-reel tape recorders.
deck (v.1) Look up deck at Dictionary.com
"adorn" (as in deck the halls), early 15c., from Middle Dutch decken "to cover, put under roof," a nautical word, from Proto-Germanic *thakjan, from PIE root *(s)teg- "to cover." Meaning "to cover" is from 1510s in English. Replaced Old English þeccan. Related: Decked; decking.