The field’s title is not really editable but there should be a title to that dropdown with the string “Cryptocurrency”.
If it is not shown, it is hidden by your theme’s CSS. You can find the label with the selector label[for=billing_cryptocurrency].
EDIT: Actually, looking at your screenshot a bit closer, it is obvious that it is a problem with CSS. The label is there, but your theme is not displaying it in the right place. This is not an issue with the text itself, but with the CSS rules. It should not be very hard to fix.