This interesting and uncommon name is of Old French origin. It was introduced into England after the Norman Conquest of 1066 and derives from the Old French "avril(l)." The month of April, ultimately from the Latin "aprilis", a derivative of "aperire", to open, has reference to the opening of buds and flowers in the spring.
The term was used as a given name for someone born, baptized or officially registered in April, or having some other connection with the month, such as owing feudal dues; it may also have been used as a nickname, perhaps with reference to the changeable weather of the month, "changeable, vacillating", or with reference to spring or youth. The surname from this source can be found as April, Averill, Averell and Avril, and early examples include: Robert Aprill' (1301, Yorkshire); Richard Averil (1322, Staffordshire); and John Aueril (1327, Sussex).
The forms Averill and Averell are also found in Ireland, where they are associated with Counties Limerick and Tipperary since the mid 17th Century, and came to Ulster at the time of the Plantation. John Averill was bishop of Limerick in 1771, but was born in County Antrim. In London, Henrye Averill married Cycelye Meryfeelde on April 25th 1585, at St. Michael Cornhill. The first recorded spelling of the family name is shown to be that of Thomas Averel, which was dated 1275, in the "Subsidy Rolls of Worcestershire.