PHRASEOLOGICAL UNITS WITH LEXEME "FIRE" IN DIACHRONICAL ASPECT
Phraseological units (Ph.U.) are popular and widely spread in different languages as they are very expressive. The analysis of their inner structure in diachronic aspect helps us to spotlight on the history, culture and traditions of different nations.
In this article we are going to describe the Ph.U. with “fire”- component in English as this nature element is vitally important for all human beings because on the one hand it gives warmth and life, on the other hand, it can be ruinous and disastrous and it can take this life away. The etymological analysis of this lexeme shows that it goes back to the Old English “fyr” which is in its turn related to Old Saxon “fiur” , Old Norse “fūrr”, Old High German “fūir” , Greek pur Derived words: “fireable ; fireless ; firer”. Apparently there might be two roots for the lexeme “fire”: *paewr- and *egni- (source of Latin ignis). The first one was "inanimate," referring to fire as a substance, and the second was "animate," referring to it as a living force such as water .
There are the following definitions of the lexeme “fire“ in Collins Cobuild dictionary: 1) the state of combustion in which inflammable material burns, producing heat, flames, and often smoke
2) a) a mass of burning coal, wood, etc., used esp in a hearth to heat a room b) (in combination) firewood firelighter
3) a destructive conflagration, as of a forest, building, etc
4) a device for heating a room, etc
5) something resembling a fire in light or brilliance a diamond's fire
6) a flash or spark of or as if of fire
7) a) the act of discharging weapons, artillery, etc b) the shells, etc., fired
8) a burst or rapid volley a fire of questions
9) intense passion; ardour
10) liveliness, as of imagination, thought, etc
11) a burning sensation sometimes produced by drinking strong alcoholic liquor
12) fever and inflammation
13) a severe trial or torment (esp in the phrase go through fire and water)
Basing on the definition analysis, we may distinguish predominantly the following shades of meaning in the lexeme “fire“: 1. nature element; 2. house heating device; 3. home comfort; 4. passion; 5. zest for life; 6. fever; 7. destroying force.
Generally speaking, it should be mentioned that in many cases the shades of the semantic meaning of this lexeme coincide in English and Russian. It can be proved at the functional level even in Ph.U. We can illustrate it in the following examples.
First of all, it should be noted, that fire for all human beings means the warmth and the comfort of home and it found its representation in the language in the Ph.U. keep the home fires burning meaning "to provide family, to keep and protect it". In English this expression goes back to the song which was popular during the Second World War.
Eg., ‘It seems to me,’ went on Ernest... ‘That we're going to hear a lot from father about keeping the home fires burning. You know what that leads to.’ ‘Reasonable 'conomy,’ said Julie... 
In Russian “fire” also symbolizes “family comfort” and it may be proved by variety wedding customs and traditions. The universality of this meaning in different languages and cultures indicates that there might be some ancient pre-historic roots.
In English and in Russian lexeme “fire” is very often connected with emotional sphere as in the Ph.U. to catch fire:
Eg., ‘I'll study algebra,’ he concluded... He took fire with unexampled rapidity. 
Eg., And every day he was more and more tempted... to see whether he could not make her catch fire, and flare up with some emotion or idea. 
The origin of many Ph.Us goes back to the Bible it can be demonstrated with the help of Ph.U. fires of hell meaning “a terrible places where sinners are tortured“:
Eg., The fires of Hell burned fiercely before his mind's eye. 
On the contrary, the place where the righteous men are located, can be poetically called fires of heaven meaning “stars“which in many beliefs and religions are connected with upper positive spheres.
In many languages there are different legends describing the way people got fire, but one of the most famous and popular is a Greek legend about Prometheus who had gifted fire to people. Due to this legend Ph.U. Promethean fire became popular and gained the meaning in many languages “a burning desire to achieve goals, best ideals”.
Everyday life exposes some practical things and situations. People know that fire can spread rapidly and it is reflected in the sheer inner form of some Ph.Us:
The Ph. U. like a forest fire means “very quickly”:
Eg., " She would... flirt like wildfire for a fortnight .
The inner form of the Ph. U. no fire without smoke shows that everything has got it consequences like in nature smoke shows that there is fire.
Eg., Mrs. MacHugh said that there was never fire without smoke .
In spite of that fact that there are some universal meanings of lexeme “fire” in many languages, there might be some national peculiarities. If we take, for example, Ph.U. Kentish fire, we will find out that it means “the sound of diapproval“. Only in diachronic aspect we can reveal its inner content. This expression goes back to the noisy meetings in Kent in 1828-29 which were directed against Catholic Relief Bill. It can be observed at the functional level:
Eg., The entry of the professor was signalled by a few rounds of Kentish fire from the heavy boots of those students who sat on the highest tier of the gloomy theatre....
To crowd it all, it should be mentioned that the diachronic analysis of Ph. U. helps to reveal their inner content and to find out many interesting facts about the customs and traditions of different countries.