Many expressions that used to be everyday are outdated today, they are inserted into speech for the sake of color or as a joke. However, even the speaker does not always understand the essence of idioms. For example, the expression "hitting the forehead" today has a very ironic connotation.
The word "beat" is quite polysemantic, in dictionaries there are from 8 to 12 meanings. The most appropriate meaning of the meaning of "hit" in the expression "hit with the forehead" is to hit something. The forehead is the forehead in the Old Russian language. That is, if you literally understand, it turns out: "banging your forehead" - banging your forehead against something.
After analyzing the use of this phraseological unit in more detail, we can conclude that they said so in two situations. The first - when they greeted, that is, weighed a low bow to the ground. The second is when they asked for something. The petitions themselves in the old days, in fact, were called petitions. They were considered official documents in Russian office work of the 15th-18th centuries. In terms of their content, they could include both complaints and denunciations, and requests. In legal proceedings, starting from the 16th century, there was a petition order - a special body that dealt with petitions.
A variant of this phraseological unit as a greeting is still preserved in the Polish language, albeit in a slightly abbreviated form. Instead of the traditional "hello" in Poland, they habitually say czołem, that is, "chelom". The history of the origin of this phraseological unit refers to the second example of its use.
In our time, the phraseologism "to beat with the forehead" is little used. The applicability of this combination ended after the events of 1917. After the country completely disappeared, in which they beat their heads on the ground with a request in the face of their superiors and generally bent their backs in front of the authorities, you can hear it in stories about the distant past of the country.
With the words "forehead" and "hit", the most commonly used combination today is "banging your head against the wall." It denotes the commission of vain actions. But a couple of centuries ago, "hitting the forehead" was quite often on the lips. This is evidenced by literary works, for example, Griboyedov's "Woe from Wit":
“The legend is fresh, but hard to believe.
As he was famous, whose neck often bent;
As not in war, but in peace they took with their foreheads -
They knocked on the floor, not regretting!"
Domestic cinematography has a vivid example, where it is clearly demonstrated how they "beat their foreheads" in front of the tsar in Russia in ancient times. This is a comedy film "Ivan Vasilyevich Changes His Profession", directed by Leonid Gaidai in 1973. Phraseologisms quite vividly reflect the history of the country. After all, they do not arise from scratch. These are a kind of elements of oral folk art, without which speech would not be so capacious.