In order to rename theme words, you can use Loco Translate plugin.

Please see below the steps that needs to be followed:

1.Install Loco Translate plugin

loco translate help

2. Go to Loco Translate – Manage translations

—select the theme and add New language

loco tranlate help2

— select the language that you have chosen in Settings-General

loco tranlate help3

— make sure that you select the exact language- Start translating

loco tranlate help4

3. Search for the words that you wish to rename

loco tranlate help5

— add the new words and save

loco tranlate help6