I have heard and seen in writing the expression "a gypsy's warning". I take it to mean "a warning of an irrational nature, along the lines of someone reading a crystal ball or tea leaves and pretending to be able to tell you all about the future". E.g.: A gypsy's warning not to apply for a job because one may die on the 10th day of the 10th month in the job in question. When I first heard the expression, I must admit I thought it might be derogatory and refer to a warning made in an insincere manner, perhaps to fool or cheat the person, and better rob them - given general anti-gypsy prejudice down the ages in Europe. But I believe the meaning is more neutral and as described above (in my 1st paragraph). I find it a bit surprising that the expression is used freely in English in our PC times... I have seen it used in an article in the FT of the UK. Comments and insight welcome.