The origins of some last names are pretty self-explanatory, whether it's Baker, Shepherd or even Rotten. But many surnames make no sense at all, at least not to the average Joe without a degree in Old English or Celtic genealogy. That’s why, according to Steven Morris at The Guardian, a team of researchers from the University of the West of England in Bristol spent four years sleuthing out the origins of more than 45,000 surnames common to Great Britain and Ireland, with 8,000 of those, like Twelvetrees and Farah, investigated for the first time in the new book, The Oxford Dictionary of Family Names in Britain and Ireland.

According to the publisher, the tome includes every last name in the island nations that has 100 or more bearers including the frequency of the name in 1881 and how common it is today.

Rod Minchin at The Independent reports that the researchers analyzed sources dating back to the 11th century to trace the history of the names. They also combed medieval and modern census documents, church registers and tax records to analyze how spelling and usage have changed over the decades. “There is widespread interest in family names and their history,” Richard Coates, one of the team leaders tells Minchin. “Our research uses the most up-to-date evidence and techniques in order to create a more detailed and accurate resource than those currently available.”

Morris says there are many names linked to professions and locations, like Smith or Leicester, but there are plenty of surnames that are head scratchers. Campbell for instance has a confusing history. In the past, researchers believed it was a corruption of the Latin phrase de campo bello, meaning “of the beautiful field.” New research, however, indicates that it is probably related to the Gaelic phrase meaning “crooked mouth.”

Another name that required revision is Hislop. According to a press release, the name is currently held by 1,630 people. Previous research indicated that it was related to an unidentified spot in northern England. But it turns out it originates from Scotland, and is related to the Middle English words hasel (hazel) and hop, which is a deep enclosed valley.

The BBC writes that the volumes show an interesting breakdown. Ninety percent of the names in the dictionary, the researchers found, were native to Britain and Ireland, with 50 percent derived from place names and 23 percent of the names coming from relationships, like Dawson (son of Daw). Surprisingly, 19 percent were derived from nicknames, including Fox, Goodfellow and Longbones, while 8 percent were derived from occupations.

The most common names include Smith, Jones, Williams, Brown, Taylor, Johnson and Lee. But there are a few outside names that are catching on. For instance the Chinese surname Li was used 9,000 times in 2011 and the Indian last name Patel is also increasing, with over 100,000 bearers.

“We're all naturally fascinated about where our family names originate from and what meaning they might have. The boom in the last decade in genealogy and the popularity of TV programmes such as 'Who Do You Think You Are?' show that knowledge about the origins of family names is so important in helping to understand our own stories and mapping out those of our ancestors,” Samuel Lambshead, Strategy and Development Manager at the Arts and Humanities Research Council which helped fund the study, says in the press release.

We’re guessing his name probably has something to do with sheep, but then again we’re not trained surname researchers.