'league-based' originates from English, specifically the noun 'league' and the past-participle/adjectival use of 'based', where 'league' meant 'an association or group (often of sports teams)' and 'base' (in 'based') meant 'to found or be founded on'.

'league' comes from Old French 'ligue' (from Medieval Latin 'liga'), while 'based' is formed from 'base' (from French/Latin roots), and the compound adjective 'league-based' developed in modern English by combining these elements to describe something founded on or organized by a league.

Initially both elements separately referred to an association ('league') and the idea of foundation ('base'); over time the compound came to specifically mean 'founded on or organized according to a league', especially in sporting or competitive contexts.