GH - Nighthawk

The digraph 'gh' is found in many English words.  If it's at the beginning of the word it has a 'g' sound.  If it's elsewhere in the word it's either silent or has a 'f' sound.  The words where it is silent are often derived from German words which have a back-of-the-throat frictive (often depicted as an 'x' in phonetic alphabets.)  You can hear this sound in German words like licht (light), nacht (night), acht (eight), or hoch (high).  When English first adopted these words probably the 'gh' was pronounced but over the years while the sound was dropped the letters were not. (Or would that be naught?)