German Kartell,
from French cartel,
from Italian cartello, placard,
from Medieval Latin cartellus,
charter, diminutive of Latin charta,
Take your pick really.
OR
Synonyms: bunch, chain, combine, conglomerate, consortium, corporation, crew, crowd, gang, holding company, megacorp, merger, mob, monopoly, multinational, outfit, pool, ring, syndicate, trust