One way to hold this word: a glass room with a heater running inside it. Outside there is frost on the path; inside the glass is fogged, the air is warm and damp, and a plant from a hot country keeps its leaves all through January. Nothing about that room is gentle — it is shut in, and it is pushed. Everything else the word does is this room with something other than a plant inside it.
From the word’s history
Wiktionary gives Middle English hothous, simply hot + house. The word has never stopped meaning what its two parts say, which is why the picture is so easy to carry into the other uses.
Wiktionary 的說法很單純：來自中古英文 hothous，就是 hot ＋ house 兩個字拼起來。這個字從頭到尾都沒有離開過字面意思，所以那幅畫面才能一路帶著走。
Wiktionary entry for hothouse, packet source_ref kaikki:3f6f69a190036ae4:1251344595 — 'From Middle English hothous, equivalent to hot + house.'
登入就可以看每一支怎麼連回核心畫面。