The initial and final sound is that hard
G found in
German,
Dutch and related languages but not in
English.
Thought there is no direct analogue in Afrikaans, there are some instructively similar words in the South African variety of Dutch:
Note that the 'ig' ending corresponds to an 'ish', 'able' or 'ive' ending in English. Gezellig means, hm ... companionable only more so. festive, but less extrovert. Maybe cosy or heartwarming. Perhaps a comfortable atmosphere in which open conversation can take place between friends.
But there is more to it than that. There is the connotation which as noted, helps define the culture.