One way to hold sideboard is to take the two halves at face value: a board standing along the side of something, off to one side of the main action. The table is where dinner happens; the board along the wall waits beside it. The truck bed is where the load sits; the boards along its edges hold it in. Each meaning is something useful placed at the edge rather than in the middle.
sideboard 可以想成就是字面上的兩塊拼起來：一片立在旁邊的板子，待在主角的邊上。吃飯的主場是餐桌，靠牆的那個檯面就在旁邊候著；載貨的主場是車斗，兩側的板子就沿著邊擋著。這個字的每個意思，都是把一樣有用的東西放在邊邊，而不是放在正中間。
From the word’s history
Wiktionary gives the etymology as simply side + board, for both the noun and the verb.
Wiktionary 對名詞和動詞都只記了一句：From side + board——就是 side（旁邊）加 board（板子）。
Wiktionary entries for sideboard (noun and verb), etymology_text: From side + board (kaikki:3f6f69a190036ae4:904239457 / :904252634)
登入就可以看每一支怎麼連回核心畫面。