The German Zitter (usually called a "Scheitholt" today, though I don't think that anyone actually called it that, beyond the Praetorius book..) was made generally without a raised fretboard, with the frets directly on the soundboard. It could have as many strings as you wanted on it, but often with one or two (or four or six!) drone strings, and one or two melody strings. It was sometimes bowed, and sometimes plucked, usually with a quill. A stick was usually used as a "noter". These were common among the German immigrants in the 18th century. They were used in small churches for musical accompaniment where organs were not available. They could be just about any shape the instrument maker wanted, but they tended to be squarish and rectangular, or tapered from the larger lower end down to the peg head.
The mountain dulcimer is essentially the same instrument, with the addition of a raised fretboard. It seems to have come about some time during the 19th century.
I have intended to try to make one, myself, for years now, but never gotten around to it.
I got a dulcimer for my dad last year, since he had injured his left hand and couldn't play guitar anymore.
