The ornamental design for a buttockregion of a pair of firefighter pants, as shown and described.
FIG. 1 is a right side elevation view of a buttock region of a pair of firefighter pants showing my new design;
FIG. 2 is a left side elevation view thereof; and,
FIG. 3 is a rear elevation view thereof.
The dashed line showing of the portions of the pants are for illustrating environment. The dash-dot-dash lines represent the boundary of the claimed design. None of the broken lines form any part of the claimed design.