Some that seem to make the most sense are as follows:
There is an old and well-founded tradition that all the MANNINGS in the whole world are descended from the 37th King of Ulster, Ireland. This King was very wealthy and was, therefore, called the "Maoin", which means riches, wealth. The Clan of Maoin was as numerous as the sands on the seashore. Saint Patrick converted them to the Catholic Faith himself.
Sometime between the tenth and thirteenth centuries many of the Maoins crossed the English Channel and settled in Southern England on the Kentish Coast and, according to English Law, they were forced to give their name an English form. They chose Manning. Some of them, dazzled by English gold, gave up their faith and soon advanced to a high position in the English Nobility. Some others chose the name Mannion.
The surname Manning is in fact of English patronymic origin, being one of those names derived from the first name of a father. In this case it is derived from the old English personal name Manning and simply denotes 'son of Manning', while Manning itself may derive from the old Norse name Menning, meaning 'able', or the old English word 'mann', a servant, hence the son of the servant.
Early recorded English instances of the name includes a reference to one Mannicus in the Domesday Book of 1086 and Algarus Manningestepsune in 1130, mentioned in Ekwall's "Early London Personal Names". Seaman Lilius Manning appears in the Pipe Rolls for Essex in 1181 and Ainulf Manning in the Pipe Rolls for Kent in 1190.
The surname Manning is on the record in Ireland from the seventeenth century and is most numerous today in the counties Cork and Dublin. It is interesting to note that while it is essentially an English surname, Manning has occasionally been used as a synonym of the Gaelic surname O'Mannin and that, for example, Cornet John Manning of O'Neill's dragons in King James II's Irish army, was an O'Mannin.
Manning is from an old Norse word - manningi - meaning a brave or valiant man; and one of the first forms of the name was Mannin; another cartography was Mannygn. One historian gives a Saxon origin for the family, which he calls "ancient and noble". According to him, Manning was the name of a town in Saxony, and form thence the family of Great Britain sprang.
Other historians make Mannheim, Germany, the cradle of the family, and begin its history with Ranulph, or Rudolph de Manning, Court Palatine, who, having married Elgida, aunt to King Harold I of England, had a grant of land in Kent, England. His name is also written de Mannheim - Rudolph de Mannheim. His place in Kent was Downe Court, and there the Mannings have been a power ever since. Simon de Manning, a grandson of Rudolph, was the first of the English barons to take up the cross and go forth to the Holy Wars. He was a companion of King Richard, Couer de Lion, and was knighted on the battlefield. We can easily see where the cross of the coat of arms comes from. At Downe Court these arms are seen graven upon tombstones of the Mannings. By the thirteenth century the family was well represented in over a score of countries and several towns bear their name - Manningham, Yorkshire, and Mannington, Norfolk.
In researching the Manning family one can find several different spellings, different branches of the family and different explanations to the origins of the name.