Rename Buddypress Profile Tab

Look at the source, you know that already. 🙂

I didn’t but I bet there is a piece of code looking like this:

_e( 'Activity', 'buddypress' );

… or …

__( 'Activity', 'buddypress' );

Follow the functions, they are wrappers for the function translate() in wp-includes/l10n.php:

/**
 * Retrieves the translation of $text. If there is no translation, or
 * the domain isn't loaded, the original text is returned.
 *
 * @see __() Don't use translate() directly, use __()
 * @since 2.2.0
 * @uses apply_filters() Calls 'gettext' on domain translated text
 *      with the untranslated text as second parameter.
 *
 * @param string $text Text to translate.
 * @param string $domain Domain to retrieve the translated text.
 * @return string Translated text
 */
function translate( $text, $domain = 'default' ) {
    $translations = &get_translations_for_domain( $domain );
    return apply_filters( 'gettext', $translations->translate( $text ), $text, $domain );
}

You see you get a filter: 'gettext' with three arguments (or parameters). Now you can use the filter to change the output.
Add this to your theme’s functions.php or to a plugin:

add_filter( 
    'gettext', // filter name
    'wpse_57673_change_buddypress_profile_tabs', // name of your custom function
    10, // priority
    3 // number of arguments you want to get
);

Now we need the custom function, that’s really simple:

function wpse_57673_change_buddypress_profile_tabs( $translated, $original_text, $domain )
{
    if ( 'buddypress' !== $domain )
    {
        return $translated; // not your text
    }

    // find the text to change
    switch ( $original_text )
    {
        case 'Activity':
            return 'My Activity';

        case 'Groups':
            return 'My Groups';

        default:
            return $translated;
    }
}