WooCommerce Checkout Tooltips
WooCommerce Checkout Tooltips – Gives you the ability to add custom tooltips to the default fields on the checkout page of WooCommerce.
Within the settings page tooltips can be enabled or disabled separately, so you dont need to have tooltips on all fields, just the ones you want. There is also the option to customise the colour of the tooltip.
To test this on the demo please add a product to your shopping cart, and proceed to checkout.