Attorney at law, is there any other kind?

I have wondered from time to time about the phrase "attorney at law." Are there other kinds of attorneys? Attorneys at arms? If not, why do we specify?

One definition of an attorney is "A person appointed to act for another in business or legal matters." See also http://www.merriam-webster.com/dictionary/attorney. This usage is seen in such phrases as "power of attorney", which employs an attorney-in-fact.

Attorney in the US sense is an abbreviation for attorney at law, or public attorney. There are different types, like the private attorney.

Attorney at law or attorney-at-law, usually abbreviated in everyday speech to attorney, is the official name for a lawyer in certain jurisdictions, including, Japan, Sri Lanka and the United States.

The term was also used in England and Wales for lawyers who practised in the common law courts. In 1873, however, attorneys were redesignated solicitors (which had always been the title for those lawyers who practised in the courts of equity)

Source: Wikipedia

Also:

In English law, a private attorney was one appointed to act for another in business or legal affairs (usually for pay); an attorney at law or public attorney was a qualified legal agent in the courts of Common Law who prepared the cases for a barrister, who pleaded them (the equivalent of a solicitor in Chancery). So much a term of contempt in England that it was abolished by the Judicature Act of 1873 and merged with solicitor.

Source: Online Etymology Dictionary

My professional license says that I am an Attorney and Counselor at Law in Washington State, USA. I represent clients in courts of law and equity, which are no longer separate courts in most states. When I achieved my Juris Doctorate, I was a law graduate and a lawyer. When I passed the bar exam, passed the background check and made the oath as an officer of the court, I received the state-issued license to be an attorney at law.

The gist of attorney is the authority to do some legal act for someone else.

An attorney-in-fact requires no education in the law. A principal appoints an attorney-in-fact as the principal's agent to perform some act with legal consequence, often in the absence of the principal. For example, a military officer assigned overseas might appoint his mother as his attorney-in-fact to conduct his banking transactions, to execute contracts for him, or to buy real property in his name.

Professors in US law schools are usually lawyers who do not have the license to practice as attorneys at law. Judges in the United States are usually lawyers, and most of them at one time were licensed as attorneys at law. Professors and judges do not represent clients, so they will often let the attorney license lapse rather than pay the hundreds of dollars every year to maintain it.