Does "希" mean Greek or Hebrew?
Yes, 希 can refer to Greek, 希腊； or 希伯来 Hebrew; But I would be very carful in using it as it may causes confusion unless the context is very clear. For example, 他會説英德希三種語言。is confusing, definitely not Spanish (西 would be used).  But is it 希腊 or 希伯来？ For minor languages (in the sense of not many people use it), we tend to use the full name: 希伯来语，希腊语，意迪绪语，... etc.  Alas, this so happened in human history: &quot;The last Mohigan&quot;; the 莫歇语 (the only person who know it passed 10 years ago), especially the languages spoken without writting.