Making a change to a string in Firefox can have impact on localizations. If you're making a change to a string, you must follow these guidelines.
Updating Entity Names
If you are changing a string such that its meaning has changed, you must update the entity or property name for the string to match the new meaning. If your changes are relevant only for English — for example, to correct a typographical error — then there is generally no need to update the entity name.
If you change the entity or property name of a string, you must also update all instances where that entity or property name is used in the source code.
If you change the entity or property name of a string, and the string has an accompanying access key, command key, or tooltip, you should update their names as well for consistency. This change is fundamental for access keys, since many localization tools use the entity name to connect an access key to its label, for example to check if it's using a character not available in the original string: given entities "useBookmark.label" and "useBookmark.accesskey", if you change to "chooseBookmark.label" due to a string change, change the access key entity to "chooseBookmark.accesskey" to match it.
Localizers usually work on the localizable files without the context of the source files including the localized strings; it is important to add comments to the localizable files themselves, too. These comments are generally referred to as localization notes. There is an established format for these notes, which is described in Localization notes.