discourse/app/assets/stylesheets/common/components/d-tooltip.scss

// ".tippy-box" is one of the classes tippy.js uses for creating tooltips
// see https://atomiks.github.io/tippyjs/v6/themes/#tippy-elements
//
// Using `data-theme~="d-tooltip"` scopes down these styles
// to tooltips created using the d-tooltip component
.tippy-box[data-theme~="d-tooltip"] {
  color: var(--primary);
  background: var(--secondary);
  border: 1px solid var(--primary-low);
  box-shadow: shadow("menu-panel");
  overflow-wrap: break-word;
}