How to add new languages to Pidgin spellchecker in Linux?

On the Pidgin site you can read that Pidgin will use any of the GtkSpell dictionaries you have installed:

https://developer.pidgin.im/wiki/Using%20Pidgin#SpellChecking

But I was confused when I searched the packages list with aptitude for gtkspell, because I only found libgtkspell, no packages with particular languages. The secret is these packages names begin with myspell-, for example to install Polish language do:

sudo aptitude install myspell-pl

I restarted Pidgin and new language was available on the list.

As indicated here:

You need to install additional spellcheckers. Navigate to your system's package management tool and search for the package hunspell-, for example hunspell-ru for Russian. If it does not exist, search for myspell-. Both hunspell- and myspell- dictionaries are supported by Mozilla and OpenOffice, so you have a good chance of finding these dictionaries for your distribution. The difference between hunspell and myspell is that the latter one is deprecated for many languages, and the former one replaces the outdated version

For many languages the way to go is:

sudo apt-get install hunspell-<your_lang>

replacing your_lang as needed.