There are as many answers as there are variations. Some chose the spelling while others had it bestowed upon them as being the way it should have been spelled. At times in America and in England it was not popular for people to even think that you might be Irish, and at those times many Mac, Mc, O, and apostrophes were dropped. In some rural areas, I think putting food on the table was more important than spelling; notice the I think. My grandfather was a direct descendant of an Isaac O'Dell. His grandfather Floyd shows up on county marriage records as Odele but his death certificate as O'Dell. I saw a picture in a county newspaper of his Uncles standing behind their mother who was seated and the brothers used different variants. I thought it was a county paper so they probably just didn't pay close attention to spelling, but when I read the article the spellings stayed true to the captions beneath the picture. I asked my grandfather O'Dell and he said the ones from the country were Odell, (which he pronounced as Odle ); the ones who thought themselves to be more refined or from town used the apostrophe; and the ones who used a capitol D, were Democrats and proud of it. My grandfather was born over 100 years ago and lived in the last century. Unless you can find someone to confirm or deny this: A legend is born!! Regardless; it is a good story and a good memory!