@fortawesome/fontawesome-free/less/_icons.less

The iconic font, CSS, and SVG framework

// specific icon class definition
// -------------------------

/* Font Awesome uses the Unicode Private Use Area (PUA) to ensure screen
   readers do not read off random characters that represent icons */

each(.fa-icons(), {
  .@{fa-css-prefix}-@{key}::before { content: @value; }
});