Surnames back in those days for commoners were based upon one of two things: the city in which you lived (So X de Eley meant that X lived in the city or town of Eley) or your profession. It's possible that your ancestors either grew to dislike the town of their birth or would have preferred to go by their profession's name.

Old name might have some bad associaton happening.

Or change from locale to proffession as mentioned by Hayabusa.

Or maybe as simple as a peasant son getting an actual trade apprenticeship. Such was a BIG, BIG thing for a dirt grubber's kid back in the day.

This line went from knights, VIPs and landed gentry in Britain all the way forward to the late 1400s, then the name changed to the common name and as you say, family status appeared to change as the world changed in the 1500s and 1600s. No more landed gentry in this line, and the name changed to Smith. A couple more centuries past that, my grandfather was homesteading on the prairie of Saskatchewan. Can't be much more humble than that!

Fascinating.

Sounds to me like someone pissed off a king or ended up on the wrong side of a war or rebellion. The previous name may have been a title used only by grant of the king. Once revoked, the family had no choice but to fall back on the family name.

Then again, there were a lot of families who had no family name, no surname, until the 1400's or 1500's. It maybe that the family still retained their ancestral title, but officially took a surname and used it for legal records. In England, titles and the names that went with them only passed on to the oldest son. The remainder of the family used the surname.

A gander at Debretts (sp?) might help you figure out what happened.

On my father's side, I spent a long time looking for a link to the DeGray family in France.

What I found was that someone by the name of "Legoues" came over, and took the name of "Grais" from the military unit he was in that was sent to Canada in the late 1600s/early 1700s.

That was changed to "de Grais", then "Degre' ", and then to DeGray.

On my mother's side is evidence of a man with the last name "Regnier" adopting the last name of his wife, which was "Brion", and then maybe a generation later changed to "Brillion".

Oh, to have been a fly on the wall during all that time, to see what happened and why...

a criminal background. He wanted to change his name but had not thought it through. As he walked in the line at Ellis Island he looked up and saw a beer sign for Miller's. From that day he and his family went by the name Miller.

Same reason with a family in my tree. Went from Maas to Hinderson and then shortened it to Hinders.

So if the name sounds the same, the spelling doesn't necessarily mean it's a different family. Standardized spelling didn't exist, and there are examples of names sounding the same but spelled differently. This often happened when a person came through an immigration point. The person writing down the name spelled the name in the manner they thought is was spelled but may have been incorrect. Same with census takers. For example, if someone of German heritage wrote down the name "Deal" it likely came out "Diehl". Someone from England may have written it "Deale". One of my friends who is researching the Deal name, came up with documents when taken together showed six different spellings of the name, but all referring to the same family.

Also, as one poster said, socioeconomic status played a role. I have one ancestor without a title who married a woman whose father had a title and no male heirs. He took his wife's name (and title). And ever afterwards, the family carried the wife's name.

on a US census form one time for a great grandfather, whose last name was Auclair.

Likely because of my g. grandfather's Canadian French accent, the census taker recorded his name as O'Clair, making it look Irish.

or because of a prominent relative of that name--see for instance the children of one Morgan Williams and his wife Catherine Cromwell, sister of Thomas Cromwell, minister to Henry VIII; they became known as "Williams alias Cromwell" and in later generations just "Cromwell". Also possibly because of association with a village or manor of that name (which, in the case of the gentry, which is the social class we're dealing with, is frequently where a surname would come from in the first place).

the name change indicates a man taking his wife's surname, to keep that surname going if she had no brothers. Or her father had a lot of money and that was the condition of allowing the marriage.