the public; the world; society
Refers to the wider world or public life, often with a nuance of the secular world outside one's immediate circle. Somewhat literary.
He threw himself into the world at large.
rivers and lakes
Original literal meaning. Now mainly encountered in classical contexts or set phrases.
Archaic sense for a retreat away from society, often associated with hermits. Not used in modern Japanese.
Originally, 江湖 referred to rivers and lakes.
In old poetry, 江湖 can mean a hermit's dwelling.
Standard kanji spelling. The reading ごうこ is obsolete.
From Chinese 江湖 (jiānghú), literally 'rivers and lakes', which came to mean the world at large or a place of retreat. The reading ごうこ is an older, now obsolete, pronunciation.