thanks for the info about 'oakes', and the correct spelling of it.
No, I didn't say anything about 'correct' spelling. There was no such thing before the late 19th century. You'll find 'darach' with 'o' instead of 'a', and with one 'r' or two, and in oblique cases you may find some other letters creeping in, or the 'a' missing from 'Mac'. All are equally 'correct'.
I found my Irish Gaelic dictionary and 'oak' is given as 'darach'. It is where the name of Derry/Londonderry comes from, and also for instance Craigendarroch on Deeside in Aberdeenshire.
I wonder why people would change their names, why not just still to the original one?
It was not unusual for people to change a Gaelic surname for an anglicised version - in Scots Gaelic, for exampler, 'gobha' means a smith, and in Irish Gaelic it's 'gabha'. The 'bh' is barely pronounced, and the surname Gow is an anglicised spelling of how 'gobha' or 'gabha' is pronounced. Some went further and changed their name to Smith.
As to why, there can be many reasons. After the Jacobite rising in 1745-6, quite a lot of people changed their names to evade the Goverment troops searching for supporters of the Jacobite cause.
Macdarrach means 'son of the oak' so it's not a huge leap from there to Oakes.
Can someone confirm if 'Scots people' is easy to navigate, I can never seem to get to grips with the Irish one?
I certainly find it quite straightforward.