The ornamental design for a toothbrushholder, as shown and described.
FIG. 1 is a top and front perspective view of a toothbrush holder showing a first embodiment of my new design;
FIG. 2 is a top and front perspective view of a second embodiment thereof, with the only difference between the first and third embodiments residing in the appearance of the front of the face portion;
FIG. 3 is a top and front perspective view of a third embodiment thereof with the only difference between the first and second embodiments residing in the appearance of the front of the face portion;
FIG. 4 is a top plan view of the first embodiment thereof;
FIG. 5 is a top and rear perspective view of the first embodiment thereof;
FIG. 6 is an additional top and front perspective view of the first embodiment thereof, with the face attachment omitted for clarity of illustration;
FIG. 7 is a top and left side perspective view of the first embodiment thereof; and,
FIG. 8 is an additional top and rear perspective view of the first embodiment thereof, with the broken-line disclosure of a toothbrush for illustrative purposes only and forms no part of the claimed design.