"small, enclosed space," 1825, the first element possibly from a diminutive of cub "stall, pen, cattle shed, coop, hutch" (1540s), a dialect word with apparent cognates in Low German (such as East Frisian kubbing, Dutch kub). Or perhaps it is related to cuddy "small room, cupboard" (1793), originally "small cabin in a boat" (1650s), from Dutch kajuit, from French cahute. OED calls it "a nursery or children's name."
early 14c., "room where wearing apparel is kept," earlier "a private chamber" (c. 1300), from Old North French warderobe, wardereube (Old French garderobe) "dressing-room, place where garments are kept," from warder "to keep, guard" (from Proto-Germanic *wardon "to guard," from suffixed form of PIE root *wer- (3) "perceive, watch out for") + robe "garment" (see robe (n.)). Meaning "a person's stock of clothes for wearing" is recorded from c. 1400. Sense of "movable closed cupboard for wearing apparel" is recorded from 1794. Meaning "room in which theatrical costumes are kept" is attested from 1711. Wardrobe malfunction is from 2004.
"an Italian sideboard," 1883, from Italian credenza, literally "belief, credit," from Medieval Latin credentia (see credence).
The same evolution that produced this sense in Italian also worked on the English word credence, which in Middle English also meant "act or process of testing the nature or character of food before serving it as a precaution against poison," a former practice in some royal or noble households. Because of that, it also meant "a side-table or side-board on which the food was placed to be tasted before serving" (mid-15c.); hence, in later use, "a cupboard or cabinet for the display of plate, etc." (1560s). These senses fell away in English, and the modern furniture piece, which begins to be mentioned in domestic interiors from c. 1920, took its name from Italian, perhaps as a more elegant word than homely sideboard.
