Shopify Customization Expert

I have special variant "Other". When the customer selects this variant, the new text field is appeared. Then, the customer enters the custom text on this field. In this case, the product has "Other" variant and "custom message" in the properties. But I want to replace the "Other" variant with "custom" message, and it should be applied on the checkout page and cart page, too. If you can help me, it would be great! Thanks