Centuries ago, the Kahuna of Ula'ula tried to unify Alola, and confronted the armies of Akala, Melemele, and Poni Island in a massive battle on the slopes of Mount Lanakila. Ula'ulan records blame his humiliating defeat not on the size or tactics of the pan-Alolan alliance, but on one key Ula'ulan regiment, which fled with their pokemon en masse almost the moment they met their enemy. Under ordinary circumstances, the Kahuna would've executed those men for cowardice, but Ula'ula needed everyone it had left to ward off Akala's own invasion. Instead, the Kahuna gave them the most humiliating punishment he could imagine without crippling the remnant of his army, and forced them to march into battle under the flag of a Wimpod.
Wimpod have a well-deserved reputation in Alola for cowardice, and some of the region's earliest oral poems make sarcastic references to how Wimpod "bravely turned their tails and fled"; such references are nonetheless the closest Wimpod have ever come to an association with courage. In their defense, it should be noted that Wimpod are larval pokemon, with all the weakness that implies: Caterpie and Wumple may bravely resist Pidgeotto or Staravia, but more often than not get eaten for their trouble. And while humans may fight for honor or resources, to the point of seeing eye contact as an invitation for a battle, they should not be too quick to assume that pokemon must necessarily do likewise.
Wimpod shy away from humans so well that only in modern times did they grasp that Wimpod are actually one of Alola's most common bug pokemon. And their much-maligned cowardice not only allows them to survive a larval stage lasting much longer than a Weedle's, but also prepares them for the hit-and-run fighting style that makes Golisopod such a menacing foe.