The ornamental design for toothbrush holder, as shown and described.
FIG. 1 is a top perspective view of toothbrush holder showing my new
design, the broken-line disclosure of a toothbrush being for illustrative
purposes only and forming no part of the claimed design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a side elevational view thereof, the sides opposite and adjacent
being identical in appearance; and,