The word "Mews" comes from Saxon times when falconry was an essencial part of a noble upbringing. The change of the plumage was referred as Mewing and during this period the birds were caged and these cages and the accomodation for the falconers was know as "Mews".
From 1377 onwards the King's falconry birds were kept in the King's Mews at Charing Cross (site of today's National Gallery - Trafalgar Square). But in 1537 when a fire destroyed King Henry's VII stables (located in the area now known as Bloomsbury) the King decided to take his horses and carriages to his Mews at Charing Cross and moved all his birds somewhere else. Was then when the royal stables became Royal Mews.
Those were the times where the King were a iconic person and the whole weath people want to be like. And if the King have his horses and carriages at a Mews we should also change the name of our stables as well. For that day on all the stables where know as Mews.
Mews lost their equestrian function in the early 20th century when motor cars were introduced. At the same time, after World War I and especially after World War II, the number of people who could afford to live in the type of houses which had a mews attached fell sharply. Some mews were demolished or put to commercial use, but the majority were converted into homes. These "mews houses", nearly always located in the wealthiest districts, are themselves now fashionable residences.