'add to cart' button suddenly changed text to 'purchase' - help to change it back!

My 'add to cart' button has suddenly changed the text to read 'purchase' and I'd like to switch it back but can't work out how. I have no idea why the text has changed!!!

I spent a while customising the 'add to cart' button using code I found on the forum, and I really don't want to change the appearance at all, just the text. Can anyone help with this?

https://www.dotandhana.co.uk/jewellery/p/cosmic-star-earrings-moon-white

Thank you so much! That was lovely and simple!