Getting non-english messages in your Sql*Plus

NLS_LANG parameter in the registry causes this.
You could get your current environment settings from the sql*Plus by:
SQL> SELECT USERENV('language') FROM DUAL;

USERENV('LANGUAGE')
----------------------------------------------------
TURKISH_TURKEY.TR8MSWIN1254

SQL> desc
Kullan²m: DESCRIBE [schema.]object[@db_link]
SQL>

You could change NLS_LANG parameter in the registry:
from
TURKISH_TURKEY.TR8MSWIN1254
to
AMERICAN_TURKEY.TR8MSWIN1254

You must relogin from sqlplus, in order to see the change.

SQL> SELECT USERENV('language') FROM DUAL;

USERENV('LANGUAGE')
----------------------------------------------------
AMERICAN_TURKEY.TR8MSWIN1254

SQL> desc
Usage: DESCRIBE [schema.]object[@db_link]
SQL>