The pronunciation of surnames in Mc- or Mac- is sometimes quite difficult to predict from the spelling. These thoughts are prompted by the name McElderry, which I give in LPD as ˈmæk əl ˌder i or ˌ••ˈ••.
But the winner of the 2009 X Factor television show, Joe McElderry (pictured), calls himself məˈkeld(ə)ri.
As we all know, the prefix M(a)c- means ‘son of’ in Irish and Scottish Gaelic. The general rule is that
• before a stressed syllable it is pronounced mək, or in a more formal style perhaps mæk; thus McBride, McDonald, McEwan, McPherson
• before an unstressed syllable it is mæk, and is itself stressed; thus McAnulty ˌmækəˈnʌlti, McAvoy ˈmækəvɔɪ, McEnroe, McIntosh, McNamara
• but before k or g it is reduced to mə, thus McCarthy məˈkɑː(r)θi, McCorquodale, McGill, McGonagall, McQueen.
The problem with McElderry, and with several other names of three or more syllables, is knowing whether the second syllable is stressed or not. The BBC Pronouncing Dictionary of Proper Names regards the El- in McElderry as unstressed (which in turn triggers stress on the prefix), but Joe the singer treats it as stressed. (Anyone from Baltimore MD? What do people call its McElderry Park neighbourhood?)
For what it’s worth, the etymology of McElderry, according to the Dictionary of Surnames (ed. Hanks and Hodges), is Mac Giolla Dhorcha ‘son of the dark-haired lad’.
Why are McIlwain, McIlwraith, McIndoe, McIntyre stressed on the ˈmæk-, while McInnes is stressed on the -ˈɪn-? Why can McElroy and McElwain, not to mention McGillycuddy, go either way?
Although these surnames are now to be found throughout the English-speaking world (Joe the singer is a Geordie), the explanation of their stress patterns presumably lies in Gaelic phonetics, and perhaps in particular in dialect differences within Irish/Scottish Gaelic. Can any reader enlighten us?