Finding a common origin for the surname Pirtle, is easier said than done. Most researchers believe that because there are only a few thousand families in the United States with the surname of Pirtle, that those whose surname is Pirtle, Pirkle, Purtle or Pyrtle, or any other slight variation, is more than likely related.
As to where they came from.....There are three theories about the Pirtle national origin. Each seems to spring from a different branch of the family, but the greatest body of formal research -- so far -- supports the first of these theories.
The German Theory. This theory is supported by historical records showing Germans with the Birkel/etc. name emigrating to the United States. It is also supported by the fact that characteristics of the German language help explain most of the various name spellings within the U.S.
The Irish Theory and the "Purtells". This lineage can be traced back to Ireland, but one historical incident, however, casts doubt on an absolute Irish origin: The Norman Conquest. The French invaded England in 1066 a.d. and ruled for about 85 years. It’s possible that the French Purtells could have married into Irish stock, but there are three problems with this theory: 1) No proof, 2) Germans and other immigrants occasionally chose to live in Ireland, and 3) The Irish Purtells are "classic" Irish: Red headed and Catholic.
The French Theory. There is no written evidence to support this theory. It’s primarily based on the fact that the French invaded Ireland and that our ancestors may have lived near a fluctuating French/German border.
Even more confusing-- there is also evidence our family came from England, Holland, Sweden, Portugal or Spain.
So, at best: Hundreds of years ago, somewhere in Germany, perhaps near the border with France, was a quiet family that pronounced its name "Burr-kuhl." The word meant "little birch" and was probably a reference to a common tree growing in the area. This practice of taking ideas for surnames from the local landscape seems to have been popular with everyone from early Europeans to the Native Americans. The Berkels were probably either poor or of modest means -- farm laborers/serfs. Since boundaries in Europe often changed, and people wandered around, the Berkels scattered across most of Western Europe in various ethnic permutations. They seem to have been fairly religious, although varying from Catholic to Protestant to Jewish.