根據'The Story behind the Idioms'網站的解釋, 這個諺語十七世紀時就在用了, 它的原句為'Talk of the devil and he's sure to appear', 但是現代英語比較常用它的前半句 － 'To talk/speak of the devil', 意思是你才講到某人, 某人就出現! 這樣的解釋比較符合中文諺語的「說曹操曹操就到」。
以上原文請見:
http://www.saberingles.com.ar/idiomstory/02.html
劍橋 (Cambridge Dictionaries Online) 及牛津線上字典 (AskOxford.com) 對此也都有詳細的解釋：
"something that you say when a person you are talking about arrives and you are not expecting them" (by Cambridge)
"speak (or talk) of the devil" said when a person appears just after being mentioned. (by AskOxford)
以上和'The Story behind the Idioms'網站的說明也是吻合的。
再來看個例句:
Apparently, Lisa went there and wasn't very impressed - oh, talk of the devil, here she is.
夠清楚了吧！
有朋友提到「玉不琢不成器」的譯法, 請教過我的老美同學後, 至少他們是沒聽過這樣的解釋。有必要請你的老師進一步說明。
另外, 牛津字典對"devil"一詞的八個解釋中, 也沒有和「魔咒」有關的定義。
devil noun 1 (the Devil) (in Christian and Jewish belief) the supreme spirit of evil. 2 an evil spirit; a demon. 3 a very wicked or cruel person. 4 a mischievously clever or self-willed person. 5 informal a person with specified characteristics: the poor devil. 6 (the devil) fighting spirit; wildness. 7 (the devil) a thing that is very difficult to deal with. 8 (the devil) expressing surprise or annoyance.