In German, the most common meaning of Riegel is bolt or fence rail. This word is derived from ancient German rigil (bolt) and even older from Latin regula (rule, rail), as W. R. Schmalstieg mentions.

Now, how does a person get the name "fence rail"? This is easy: The word Riegel also means a mountain ridge or crest (which is lengthy shaped like a bolt or rail). A peasant who lives on a crest is often called the "Riegelbauer" or the "Riegeler".

But the history is different with our family line. As we found from the Becherbach registers, the spelling "Riegel" was not used in our family until 1680. Instead, we find that the earliest spellings have been Riehl, and even earlier Ruell and Reul:

Riegel (Becherbach 1680 and later)
Riehl (Becherbach, 1666, 1676)
Riehell (Becherbach 1662, 1665)
Ruell (Piesport 1624)
Reul (Piesport 1556)

This shows that our family name has the different root Ruell/Reul and was adapted over the times towards the German word Riegel. The reason for this was, that our ancestor Mattheis moved from Piesport to Becherbach where people speak a different dialect and did not understand the original pronounciation Ruell.

The very same happened also to a person named Mattheus Ruell, later Matheus Riehl (!), born abt. 1551 in Barr, Alsace, France. See: here (This person is not "our" Mattheis and not connected to our family, as far as we know)

On the other hand, the surnames Rühl and Reul are not unusual today in Germany. Obviously the original spelling has "survived" in some family branches. This opens a new wide area of genealogy research.

According to our onomatologists, the names Rühl/Ruell/Reul are not derived from the meaning "bolt" or "crest", but have another root:

Family surnames have not been used in Europe until the late middle age, about 15th century. Before this time, people only had first names and an "attribute name", describing the person's personality or profession or descendance, like Charles the Great, or John Peters-son. After the 15th century, the attribute name, which often was the father's first name, became the family surname. This was probably the case with our name Ruell. We know a medieval German fist name "Hruodillo" (="the glorious"). Some modern first names like Rudolph and Rudiger come from this. [Source: Gottschald, Deutsche Namenskunde]

This first name Hruodillo is believed to be the origin of the surname Ruell, where our surname Riegel comes from, as well as of the surnames Reul, Riell, Ruhl, Riffel, Ritschel and many others. [Source: Linnartz, Unsere Familienamen]

The following diagram shows the evolution of the names over the times: