The ornamental design for a toothbrush handle, as shown and described.
FIG. 1 is a front perspective view of toothbrush handle in color showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a side view thereof;
FIG. 4 is a second side view thereof; and,
FIG. 5 is an enlarged view of the toothbrush handle shown in isolation for clarity.
The broken line immediately adjacent to the shaded area represents an unclaimed portion of the boundary of the design. The broken line showing of the remainder of the toothbrush is for illustrative purposes only and forms no part of the claimed design.