Using Loco creates a custom translation file and this will need to be saved in the custom location to be protected from updates. The Loco documentation explains the custom location. The downside is that the site will no longer benefit from future automatic updates to translations. The custom translation will need to be updated by the site developer whenever Woo introduce new strings. This could be a burden.
Instead, consider using Say What?
https://www.ads-software.com/plugins/say-what/
which is useful for changing the odd string.
Dashboard > Tools > Text Changes
Settings:
Original string: Coupon code
(what you get when the site is in US english, ie the default language, must be exact)
Domain: woocommerce
Context:
(blank)
Replacement string:
(your choice here)
Original string: Town / City
Domain: woocommerce
Context:
(blank)
Replacement string:
(your choice here)`