 It has also been suggested that the rhyme records the attempt by King Charles I to reform the taxes on liquid measures . He was blocked by Parliament , so subsequently ordered that the volume of a Jack ( 1 / 2 pint ) be reduced , but the tax remained the same . This meant that he still received more tax , despite Parliament 's veto . Hence " Jack fell down and broke his crown " ( many pint glasses in the UK still have a line marking the 1 / 2 pint level with a crown above it ) " and Jill came tumbling after " . The reference to " Jill " ( actually a " gill " , or 1 / 4 pint ) is said to reflect that the gill dropped in volume as a consequence . 
