A nozzer is the name given to a new entrant in the Royal Navy (RN) undergoing Part 1 basic training. The origins of the word have been lost to history but a couple of suggestions have been made, outlined below.
A boy entering the service was given the title 'nozzer' because being new to the ways of the Navy, he was prone to say 'no sir' to commands, and this was corrupted into 'nossir' which evolved into nozzer.
The other explanation is that an instructor called Parker was responsible for looking after the New Entries in the Annexe at HMS Ganges (alias Shotley Barracks) and because a rating with the surname Parker is nicknamed Nosey, so 'Nosey's boys' became 'nozzers'.
The problem with the last item is that Lionel Yexley refers to the nozzers in his autobiographical book about life on the lower deck in the Victorian Navy. Since this pre-dates the establishment of Shotley Barracks, this explanation is implausable. Many years ago this writer also read a Victorian autobiography (possibly by 'Jack Nastyface') which referred to nozzers as 'nossers'.
A possible explanation lies with the origins of several naval words, which are in fact Scandinavian words witheither dissimilar or identical meanings to their usage in the RN. Examples of this include skive, skate, and with a different meaning, the Icelandic word Skran. In Danish nosser is a vulgar term used in colloquial Danish for 'balls' as in testicles. It is therefore possible that the word nozzer has Scandinavian origins.