By default, Terminal sets the locale environment variables to match the currently selected language and time/date/number formats that Terminal is using, which is selected via
System Preferences > Language and Text
(That's the name on Lion. On earlier systems the exact name of the preference panel may vary.)
A temporary solution is to drag English to the top of the list of languages, then open Terminal, then move Lithuanian back to the top. Then only Terminal will be in English. However, it will reset to Lithuanian if you Quit and restart Terminal.
A persistent approach is to tell Terminal to not set the locale environment variables, by turning off
Terminal > Preferences > Settings > [profile] > Advanced > Set locale environment variables on startup
Then the locale will default to "C" with no language specified, and most programs will then default to English.
Note that turning this off means that some programs won't be aware of which character encoding Terminal is using and will assume that it's ASCII or ISO-Latin-1 only. So if Terminal is using UTF-8 (the default), those programs may or may not behave as desired.
If this is mostly about
wget, I recommend that you make a copy of the default settings profile, turn off the locale setting in your custom profile, and only use that profile when using
wget, so that you can continue to use UTF-8 with full support when using other programs, using the default settings.
As others have mentioned, you can also override the initial locale settings supplied by Terminal in a shell startup script. For zsh, put it in ~/.zshrc. For bash, use ~/.bashrc (and if you don't already have one, create a ~/.bash_profile that runs ~/.bashrc).
See x-man-page://1/locale for more information about each of the locale environment values.
However, if you were to merely
unset LANG or set it to "C", that would normally apply to all of your shells and programs, whereas most of the time you probably want to use UTF-8 and have Terminal set the locale variables to match, to get the highest degree of cooperation, fidelity and functionality.
Therefore, if you're going to go that route, I suggest you write code to edit, rather than replace, the initial values, so that you preserve the encoding information ("UTF-8") and merely force the language to English, rather than setting the variables to "C".
For example, this works in zsh and bash:
# Replace Lithuanian with English
LANG="lt_LT.UTF-8", this will change it to
LANG="en_US.UTF-8". I don't have
wget available to test this, but this should suffice.
Doing it this way means that if you change the character encoding preference in Terminal, you won't override that in your shell startup script.