Nut: from the German
nut, (pronounced
noot)
"
nf.
mortise, recess or groove in a piece of wood or another material
that fits together with a corresponding projecting piece of material,
joint, slot,
Hmm, so the
noot is actually the recess at the starting end of the fingerboard where the
nut sits into. Just that the actual "projecting piece of material" sitting inside the
nut eventually came around to become the nut.
Or maybe it's the string "grooves" or
noots in the bone piece sitting in the
noot at the starting end of the fingerboard that gave the bone piece the name
nut.