Why a mongrel language? Well, this is no insult to either English speakers or non pedigree dogs, it is simply that, like mongrel dogs, it has a strong eclectic background which enables it to adapt to changing circumstances.
The Celtic languages which were originally spoken in Britain were gradually driven west and north as the Celts retreated before Saxon and Viking invaders to their shores and can now be heard only in parts of Cornwall, Wales, Scotland and Ireland.
English originated from a Germanic branch of the Indo-European family of languages and has three layers of vocabulary laid down over the centuries: The Anglo Saxons spoke Old English. The arrival of the Romans and Christianity introduced Latin and finally the invasion of the Normans in 1066 brought French.
Anglo Saxon is still recognisable being comprised of small basic words like a,the, this, that, but, then, under, over etc. and picture words like food, father, night sun and house. Also verbs which express basic living also remain such as fight, sleep, eat and so on.
The Old Norse spoken by the invading Danish Vikings shared much of the Old English vocabulary but they added some of the harsher sounds in English with the sk and sc sounds heard in words like scrub, whisk and sky.
When William the Conqueror arrived he and his nobles spoke French while his subjects continued to speak Old English, but gradually the language of the court changed, bringing new words into the English vocabulary. Edward III was the first king to address Parliament in English. By the time of Chaucer (1400) a form of Middle English had evolved as evidenced in The Canterbury Tales. When Shakespeare wrote his plays, in the 16th century, the language had become recognisable modern English.
Two hundred years later Samuel Johnson produced the first Dictionary of the English Language.
So there we have it, a mongrel language integrating many other languages, because English has continued to draw into itself the language of many nations. When people say "It is all Greek to me" there is some truth in it because some of it really is. Consequently the language is rich with synonyms, the derivation of many being lost with the passing of time/age/epoch (English, French, Latin). You can take your choice!
As for the problems this has brought about with spelling and pronunciation - well that would be material for another article.
English is spoken as a first language by 340 million people, second only to Mandarin.
