Tonewood
The wood used in dulcimers must have special qualities that create the acoustic properties so prized in premier stringed instruments.
Wood which meets all these criteria is capable of shaping the voice of a musical instrument, and is properly called the tonewood.
There is a wonderful article on the structure of wood, and why woods have the characteristic look they do, on William Cumpiano's wood page. Bill Cumpiano is an internationally known luthier, teacher, and writer on guitar building, and his site is worth visiting by aspiring luthiers.