'Aquarius-related' is a Modern English compound formed from Latin 'Aquarius' (the name of the constellation and zodiac sign), where Latin 'aqua' meant 'water' and the suffix '-arius' meant 'pertaining to', combined with English 'related' (from Latin 'relatus' via Old French).

'Aquarius' passed into English from Latin (via Medieval/Neo-Latin) as the proper name for the constellation and zodiac sign; 'related' comes into English from Old French/Latin roots ('relater'/'relatus'); the hyphenated compound 'Aquarius-related' is a Modern English formation used to describe connection to that sign or constellation.

Initially 'Aquarius' in Latin literally meant 'water-carrier' or 'water-bearer'; over time it became the established name of the constellation and zodiac sign, and compounds such as 'Aquarius-related' evolved to mean 'connected with that sign or constellation' rather than the literal water-carrier sense.