The ornamental design for a nametagholder, as shown.
FIG. 1 is a perspective view of the name tag holder showing our new design.
FIG. 2 is a side view of the name tag holder with a name tag inserted therein.
FIG. 3 is a front view of the name tag holder with a name tag inserted therein.
FIG. 4 is a side view of a name tag holder; and,
FIG. 5 is a front view of a name tag holder.
The broken lines showing a name tag and a name tag stand are included for the purpose of illustrating the environment of the design and form no part of the claimed design.