The Scissor Factory FAQ's:

      How We Size:

      The scissors lengths listed do not include the finger rests! Only from the tip of the scissor
      to the back of the finger rings. The German method included the finger rest, but since the
      popularity of screw on finger rests, the scissor length measurements no longer include them.
      (Ex: 5.5" scissor with finger rest used to be the standard length used for tests etc. This same
      scissor would now be considered a 5" as pictured).

      What scissor length is good for you? Some people measure the scissor blade length with the user's
      palm or finger length. There are many different techniques, all of which are for the most part useless,
      since the proper length is simply what feels good to you! For most female hair stylists, 5" was the
      traditional length and barbers liked 7.5". But these traditional lengths have now changed as cutting
      techniques evolve and develop.

      What is a Scissor

      The word "scissor" apparently comes from the Latin word "cisoria," meaning a cutting instrument,
      and the spelling is due to a confusion with the Latin word "Scissor," a form of the verb "scinder,"
      meaning to cut. The word appears in Old French between 842-1300 A.D. as "Cisoires," from which the
      Modern French word "Ciseaux" derives. In late Middle English, about 1400 A.D., there is found reference
      to "sisours" and "cysowres."

      The word "shears" apparently has a quite a different derivation, originating from the Germanic/Teutonic
      root "Sker," which later changed to "Skeresa." In Old English, the word became "Scear." The word in
      German is today "Schere."

      Today both words, shear and scissor are being used in the English language. A scissor is up to 6" in length
      and has two finger holes that are similar in size. A shear is anything longer than 6", or a scissor that has
      one finger hole that will accommodate more than one finger.