.wp-block-better-button-betterbutton a {
  position:relative;
}
.wp-block-better-button-betterbutton a span {
  display:none;
  position:absolute;
  background:#fff;
  color:#000;
  top:110%;
  left:0;
  width:100%;
  text-align:center;
  padding:5px;
  font-size:12px;
}
.wp-block-better-button-betterbutton a:hover span {
  display:block;
}