Ó Creachmhaoil is an Irish surname. The name is often anglicised as Craughwell, and Crockwell. It was largely unknown outside of the south-east of County Galway, where the village of Creachmhaoil is also found, until the latter end of the 19th century when emigres established branches of the family which still thrive in Newfoundland, Bermuda, Cornwall, Ohio and Berkshire County, Massachusetts, among other places. Documentation on the origin of the surname is not recorded, but it is doubtless connected to the village. Notable bearers of the name include American painter Douglass Crockwell, Bermudian parliamentarian Shawn Crockwell, JP, MP, Bermudian footballer Mikkail Kristopher Crockwell, Bermudian cricketer Fiqre Crockwell, English cricketer Leslie Crockwell, Guinness World Record holding rower Matthew Craughwell, Newfoundland-born author Marion Anderson (born Marion Crockwell)  and American author Thomas J. Craughwell.
Ó, in Irish surnames, indicates a grandson or descendant of the person whose given name it precedes (as in Ó Briain: grandson of Brian). Creachmhaoil is not used as a given name in Ireland, and is actually a toponym, composed of two Gaelic words.
Creach, which is related to craig, and creag, and the English word crag, refers to a rock (with which word it rhymes), or the bare rock crest of a hill (related words are cruach, for a mountain, pinnacle, or a rounded hill that stands apart...or for any type of pile, or heap, and 'cnoc', for a hill or eminence). An alternate etymology of creach is plunder, presumably in reference to herds of cattle, which were often targets of thefts and cattle raids amongst the Gaels. The usual Gaelic word for cattle is crodh, often Anglicised in place-names as crow, although the words cro, crocharsach, and crò are all connected with sheep, sheep enclosures or meadows.
A maol is a round-shaped hill or mountain, bare of trees. It is anglicised as mull, and is common in Irish and Scottish place names such as the Mull of Kintyre. Gaelic spelling rules require that maol, following creach, be lenited; that is, an h is inserted after the first letter, providing the first letter is a consonant (and not an l, n, or r). This h makes the preceding consonant silent, or changes its sound (mh, or bh, for instance, are silent or sound like an English v or w). Gaelic spelling rules also require that, with the first letter lenited, the last vowel should be slender (an i, or an e). As both vowels in maol are broad (a, o, u), an i is inserted after. These two changes alter the sound of maol (rhymes with mull) to mhaoil (rhymes with uell, or well). The sound of the two word together, therefore, sounds to an English ear like Crockwell, or Craughwell, and it is Anglicised thus (the Gaelic personal names Seán (John) and Seamus (James) became Iain and Hamish in Scotland by similar means).