Below is the Wikipedia explanation of the English phrase:

"Speak of the devil" is the short form of the idiom "Speak of the devil and he doth appear" (or its alternative form "speak of the devil and he shall appear."). It is used when an object of discussion unexpectedly becomes present during the conversation. It can also be used about a topic that quickly becomes relevant, such as the onset of rain or a car breaking down. Used in this sense it can be seen as an alternative to the phrase "tempting fate".

Deriving from the Middle Ages, this proverb (which was, and to a certain extent still is, rendered as "Talk of the Devil...") was a superstitious prohibition against speaking directly of the Devil or of evil in general, which was considered to incite that party to appear, generally with unfortunate consequences. Its first printed usage in modern English can be found in Giovanni Torriano's Piazza Universale (1666), as "The English say, Talk of the Devil, and he's presently at your elbow."

The phrase lost its overt message during the 19th century, during which it became a warning against eavesdroppers ("No good of himself does a listener hear,/Speak of the devil he's sure to appear"), and by the 20th century had taken on its present meaning."

By this explanation the phrase was originally more akin to the Yiddish "kina hora", i.e., don't bring on something bad by talking of those things, but is now used simply to designate an unexpected appearance of someone or event. Which of these meanings does the Yiddish phrase have? If the latter, i.e., an unexpected appearance, then the origin of the phrase seems to me pretty obvious: the coming of the messiah, though hoped for and anticipated in an obligatory and general sense, is not really expected on a daily basis. Thus, also, not surprisingly, the expression contains a certain irony.