From Old English trēg 'flat board,' from PIE *dóru 'wood, tree' — a tray was originally a flat piece of wood.
A flat shallow container with a raised rim, used for carrying food, drinks, or small items.
From Old English trēg, trīg 'flat board, tray,' from Proto-Germanic *trewą 'wood, timber,' ultimately from PIE *dóru 'wood, tree.' A tray was literally a flat piece of wood — the word is a cousin of 'tree' and 'true' (originally 'firm as a tree'). Key roots: *dóru (Proto-Indo-European: "wood, tree").