The Story behind Mothering Sunday:

During the 16th century, people in the UK used to return on the 4th Sunday in Lent for a service to their ‘mother church’ - the main church or cathedral of the area. This was either the church where you were baptised, or the local parish church or more often the nearest cathedral. Anyone who did this was commonly said to have gone "a-mothering", although whether this term preceded the observance of Mothering Sunday is unclear.

In later times, ‘Mothering Sunday’ became a day when domestic servants were given a day off to visit their mother church, usually with their own mothers and other family members. It was often the only time that whole families could gather together, since on other days they were prevented by conflicting working hours, and servants were not given free days on other occasions.

Children and young people who were given this day off so they could visit their families, would pick wild flowers along the way to place in the church or give to their mothers. Eventually, the religious tradition evolved into the Mothering Sunday secular tradition of giving gifts to mothers. (fromyoutome.com)