"This very interesting surname is recorded in a number of spellings including Machan, Maughan, Maun, Mawne, Meighan, Meighen, Meegen, Meugens, Mineen, Mohan, Mahan, Moan and probably others. It has at least three possible origins. It is said that however spelt it can be Scottish, English, Irish, Welsh, or even Dutch - German, and if so, all seem to have overlapped in the registers of Europe as well as the British Isles, through the passing centuries.
"If Scottish it is of medieval origin, and a locational name from Machan, an old parish in the county of Lanarkshire. This is named from the pre 10th century Gaelic word "machair", meaning river plain. As an example William de Maghan of Lanarkshire rendered homage to Edward 1st of England in 1296.
"The second possibility is that the name can be Irish, and a form of the Old Gaelic O' Mochain. This is from "moch" meaning early or timely. Two notable branches of O' Mochain existed in Connacht, one at Kilmacduagh in County Galway, and the other at Killaraght, in County Roscommon. Gregory O'Moghan was Archbishop of Tuam from 1372 to 1385.
"Thirdly it may be Welsh and if so is a locational name from places called St. Maughan or Machen, in the former county of Monmouthshire. Early examples of church recordings include on July 18th 1581, Lancelot Maughan married at St. Nicholas church, Durham, and John Maun and his wife Elizabeth, at St Sepulchre church in the city of London, on March 27th 1751. The first recorded spelling of the family name is shown to be that of David de Machan. This was dated 1214, in the Episcopal Register of Glasgow, during the reign of King Alexander 11 of Scotland, 1214 - 1249.
"Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling." http://www.surnamedb.com/Surname/Maughan
"There are a number of different theories on the origin of the Maughan surname. In medieval documents the Welsh village of Machen (near Caerphilly in south Wales) was written as Maughan. This spelling shows the "gh" substitution for the Welsh "ch" as noted in other examples. Although there may be one, I am not aware of another Machen outside of Wales so it would seem that the modern name Maughan has a Welsh origin.
"Also in Monmouthshire (southeast Wales) St. Maughan, St. Maughan's Green and references in Cornwall at St. Mawgan-in-Pyder." http://atthesugarshack.ca/maughan/surname/maughan/maughan.html