upset the apple cart 復習

　Washington (CNN) The United States and Canada will co-host an international summit on the North Korean nuclear threat in Vancouver, British Columbia, on Tuesday, as tensions on the Korean Peninsula settle into a steady simmer while direct talks between the north and the south continue.
　The summit comes at a critical time. But with diplomats' attentions absorbed by the delicate talks between the two neighboring countries -- which were initially focused on North Korea's participation in the upcoming Pyeongchang Winter Olympics but have since broadened -- some analysts are skeptical that much will come out of the Vancouver meetings.
　"I'm sure, given the circumstances on the peninsula right now, that the attendees to that meeting will be very careful about what they say publicly," Joel Wit, of the US-Korea Institute at the Johns Hopkins School of Advanced International Studies, told reporters last week, "because I think most of them there would not want to 'upset the apple cart' in any way."

http://edition.cnn.com/2018/01/15/politics/tillerson-vancouver-north-korea-meeting/index.html

　今回取り上げる表現は、upset the apple cart です。
　まず、この意味を考えると「りんごの入ったカートをひっくり返してしまう」と直訳ができます。upset にはよく使われる “to make someone feel unhappy or worried” の意味以外に、 “to push something over without intending to” とも定義することができます(LDOCE)。「しかしこれでは文意にあいません。そこでLDOCEを引いてみると “informal to completely spoil someone’s plans” と記載されていました。つまり、「人の計画を完全にダメにする」という意味だとわかります。
　次に語源です。これに関して英英・英和共に詳しい記述がありませんでしたが、英辞郎 on the Web に「せっかくリンゴを手押し車にきれいに積んだのに、ひっくり返してしまう様子から。」と記載がありました。各自辞書を確認してみてください。(OkaUchi)

cf. https://eow.alc.co.jp/search?q=%22upset+the+applecart%22