The hammered dulcimer originated approximately two thousand years ago in the Middle East. The dulcimer is mentioned in the Bible in the book of Daniel 3:5, 10, and 15 where King Nebuchadnezzar used the dulcimer "in symphony" with other instruments to command Shad'rach, Me'shach, and Abed'-Nego to worship the golden idol he had created. From it's origins in the Middle East, it is now found in various forms and by various names throughout Asia and Europe.
The name "dulcimer" comes from the Greek words for "Sweet Melody" (dulce-melos). Its name in other languages is often descended from the Greek word "psalter", which means to pluck. This is a misnomer, as even the psalterio, the Italian dulcimer is struck with mallets. In Germany, the hackbret capitalizes its name on the fact that it is struck with mallets, as its name means, "chopping block."
Many European dulcimers, such as the cimbalom of Hungary, have individual bridges for each string course. A course is a pair, three, or four strings used to sound one note. Every note on a dulcimer has multiple strings for each note. This adds volume, and fortifies the strings' ability to hold pitch while under the fire of hammers.
American dulcimers most often have long bridges that run the length of the sound board and hold twelve to twenty-two courses. Often, dulcimers are categorized by size: 12/11, 15/14, 16/15, 21/21, 17/16/8. These numbers refer to the number of courses (notes) per bridge. The first number is the number of courses on the treble (center) bridge. The second number is the number of strings on the bass (right) bridge. The third number refers to a sub bass bridge used on the left side for extreme low notes or high chromatics. (See the Anatomy of the H.D. page for an illustration.)
Chromatic hammered dulcimers are designed by individual builders to add chromatic (sharp and flat notes) that do not naturally occur on a hammered dulcimer. These additions are not standardized and vary greatly from builder to builder.
The hammered dulcimer shares its last name with an American instrument, the lap dulcimer (Appalachian dulcimer, or mountain dulcimer). These instruments are not related- other than sharing a similar repertoire. The hammered dulcimer belongs to the zither line of the string family of instruments. Zithers all have strings that run the full length of the sound board in varying lengths and tensions. The lap dulcimer belongs to the lute line of the string family. Lutes have strings that traverse the soundboard and are extended away from the body of the instrument by a neck, and do not vary the lengths of the strings. The latter excludes lap dulcimers from the zither family.