This is probably the question I get asked the most and unfortunately there does not appear to be a clear-cut answer. There are a number of theories, some more likely than others.
According to David Postles' "Origins of English Surnames" book (ISBN: 978-0904920345) it is suggested that the name is derived from "Poutrel" which is described as being "metonymic or occupational name for someone responsible for keeping horses or a nickname for a frisky and high-spirited person. From Old French. Poutrel, colt (LL. Pultrellis, from Pullis, young animal) Variations are, Puttrel, Poutrel, Potterall, Pott(e)rill, Powdrell, Powd(e)rill, Purtil."
Another possibility that is given credency by the fact that the further back you go the more common the instance of Bottrell/Botterell/Botterill and Bottrill becomes. The name Bottrell would appear to be of Norman origin from c1066, and has a number of possible interpretations. Some sources link it to an area of Normandy called "Les Bottereaux" which still exists to this day, approximately 70 miles to the west of Paris. The web suggests that "Les Bottereaux" roughly translates as "Place infested with toads"(!)
In 1302 the name appears again as "Boterelescastel" (referring to what we now call Boscastle) after its owner, William de Botereus, whose family apparently took their name from Les Bottereaux. Alternatively the surname may have been applied to describe someone who has a toad-like complexion (nice!).
The first mention in the UK appears to be from 1155 in Lincolnshire in documents related to the Danelaw which refer to a "Hamo Boterel". Going forward to 1203 in the Curia rolls there is a mention of a William Boterell and a place called Aston Botterell. Later in 1589 there is a reference in the Hillmorton (Warwickshire), parish registers of John Botterell acting as a baptism witness. A little closer to home I've found references to Botterell and Botoler in the Chrishall parish registers dating from c1680.
The Bottrell name may also be a corruption of the occupational name "Buttery", a keeper of provisions. This word is itself derived from the French word for cask or bottle: "boterie".
A common theme through all of the theories and ideas I've seen so far is that the name is from the Normandy area of France and was introduced to the UK during the Norman conquests. The three main candidates are:
I have been able to go back via son-to-father as far back as the mid 17th Century and allowing for slight variations of spelling (Potterill, Pottrill, Potterell) the name has been quite static. There are even records of the name as far back as 1550 with the "correct" spelling. Unfortunately I do not believe there is any way to go any further back in time than this point, so this question will, I suspect, remain unanswered.
This is another favourite cash-cow of some Internet companies, the fact is that coat-of-arms were not granted to families, rather they were granted to a male person and was handed down from father to eldest son. If the eldest son dies then it passes to the second eldest and so on, much like the ascention rights to the throne. If there is a coat-of-arms in the family somewhere that we would be eligable to use it would belong to William Cyril Pottrell, being the eldest in the paternal line.
I have not done much in-depth research into this area as the College of Arms, the main authority on coats-of-arms, charges a hefty price (£250) to conduct a search of their records. However, given that the surviving branch of Pottrells is descended from a mixture of paupers, farmers and blacksmiths, I think it is a pretty safe bet that none of our ancestors piqued enough attention from the powers-that-be to a degree that would warrant being awarded a coat-of-arms!
The closest thing to a coat-of-arms that I have come across is a merchant's token (See image above, courtesy of Kevin Powdrill) belonging to a John Potterell of Oakham, Rutland who was an apothecary, akin to the modern-day pharmacist. The crest on this token looks remarkably similar to the description being pedalled by the coat-of-arms companies on the web: "a crest with a bend three fleurs-de-lis". John belongs to a group of "Potterells" that I have yet to find any link to, but they would appear to have been quite well connected (A John Potterell married Elizabeth Flamsteed in 1655, who in turn was related to "that" John Flamsteed, first Astronomer Royal).
Until I find a link to this group, I have to consider that that their surname may be a fluke or that it is a corruption of Powdrill, which was more common in the area at the time. It's equally possible that they are related, but that the link lies beyond the earliest records I have found to date.
Like most genealogists who keep records on their computer I use a piece of software that is capable of exporting a family tree in what is known as a GEDCOM file. I then pass that GEDCOM file to a small utility that converts the GEDCOM file into XML, a modern file format that stores information in a logical and accessible manner. The site then queries that XML file and displays the results. The code I use to query the XML file is an ongoing development but it has reached the point where I am happy for it to function as the website.
If you are a genealogist and would like something similar for your family tree, drop me an email.