Markup: templates/output/04-elements/forms/button/button-arrow-left.html
<!-- START BUTTON WITH ARROW RIGHT-->
<button class="btn btn--arrow btn--arrow-left" title="This is a default title text">
<svg viewBox="0 0 13.455 24.081" role="img" aria-hidden="true" focusable="false">
<use xlink:href="Images/svg/sprite.symbol.svg#icon-chevron-left"></use>
</svg>
</button>
<!-- END BUTTON WITH ARROW RIGHT-->
Source:
assets/sass/04-elements/_elements.forms.scss, line 886