In medieval times people visited the 'mother' church the Cathedral.
On Mothering Sunday it was a practice to visit your mother and give her gifts of flowers usually Violets or Primroses and cake traditionally a Simnel Cake decorated with crystallised flowers. (if this cake is eaten at Easter it is decorated with eleven marzipan balls to represent the apostles - Judas not being included).
People who worked in service i.e live-in servants were given the day off.
Now I know why I had three sons - it gives me a sporting chance of getting at least one Mothers day card!