How to change all iterations of a string to another word?
Method 1: Edit settings.php file

Pros


Quick method for small number of strings.
Less accessible in cases where you want to retain some control even after granting administrator access.


Cons


English only.
No admin pages, requires access to files on server (FTP / SFTP / SSH). 
Difficult to delegate changes to non-developers.


Procedure


Edit settings.php for the site in question.


You'll need to either download the file, edit it, and re-upload it, or edit it in place on the server. Of course, make a backup.
Either way, you'll probably need to temporarily change the permissions of the file and its containing folder to to give you "write access". Be sure to take note of the permissions and change them back to what they were afterwards.
The default settings file is in drupal_root_folder/sites/default/settings.php

Look for this code at the bottom

# $conf['locale_custom_strings_en'][''] = array(
#   'Old string 1'      =&gt; 'New string 1',
#   'Old string 2'      =&gt; 'New string 2',
# );

Remove the comment marks ('#') and add string replacement assignments:


Method 2: String Overrides module

Pros


Admin page for managing string replacements.
Uses access permissions. Easier to delegate management of replacements.


Cons


Yet another module to install, update, and administer.
Possible performance hit and more difficulty to deploy (stores replacements in the database).
Uses access permissions. Harder to restrict changes when you have to give administrator access to others.


Procedure


Install and enable the module.
Follow the instructions / documentation for adding string replacements.


Method 3: hook_boot()

Procedure


Implement the hook_boot()
Use the same array as in the settings.php.

/**
  * Implements hook_boot().
  */
 function mymodule_boot() {
   global $conf;
   $conf['locale_custom_strings_en'][''] = array(
     'Old string 1'      =&gt; 'New string 1',
     'Old string 2'      =&gt; 'New string 2',
   );
 }



Method 4: Replace all the strings in the database

Procedure


Dump the database to a text file.

mysqldump -u user -p databasename &gt; ./db.sql

Run a sed command to find/replace target string

sed -i 's/oldString/newString/g' ./db.sql

Reload the database back into MySQL.

mysql -u user -p databasename &lt; ./db.sql



Note: All commands are bash commands on Linux, but you can replace them with another method.

References:


https://www.drupal.org/node/522036
https://stackoverflow.com/q/11839060/3653989