"The blue apron has been an industry trademark since 1540. The Butcher's Guild, an association of butchers in York, England dictated that a butcher's uniform or livery should include a hat, coat and apron.
WHAT DO THE COLOUR AND STRIPES MEAN?
A broad stripe apron signifies a master butcher. A lone broad stripe indicates the butcher works without any form of apprenticeship. A broad stripe accompanied by a thin line signifies the butcher trained through a five-year apprenticeship. Three stripes symbolise the master is training apprentices. The Butcher's Guild, an association of butchers which began around the 10th century determined the apron's colour. Called Butcher's blue, it's the colour of the Butchers Guild's crest and, coincidentally, the best colour to conceal stains."
-via SMH.
The firm
Rushbrookes started making aprons for the butchers of
Smithfield Market in 1837 and claim to have instigated the iconic stripes at that time. All Rushbrookes products (as above) are still manufactured in England at their Oxfordshire factory.