When I was small, elderly relatives used to invoke the word keneinahora to qualify certain cheerful or optimistic statements, eg Shes a clever girl, keneinahora, or Spurs won again on Shabbos, keneinahora.
It was a long time until I realised that keneinahora actually meant something.
It is a Yiddishised running-together of kein ayin hara. Kein means no or without in German and Yiddish, whilst ayin hara refers to the evil eye in Hebrew.
The evil eye is an ancient Jewish superstition. Good fortune should not be celebrated too loudly and ostentatiously, lest it draw the attention of the evil eye a spiritual force that would snatch away our blessings.
To this day, there are widespread Jewish traditions whose rationale is to avoid the evil eye, such as the practice of not calling up members of one family to the Torah consecutively, or of people whose parents are both living leaving the synagogue during Yizkor, the memorial prayer for the dead.
Some ridicule such customs as archaic and irrational. In their defence, one can say that they have a moral dimension. Not flaunting ones good fortune in other peoples faces is admirable even if the result is to re-inforce a superstition.