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early 14c., "to gather, assemble" (transitive and intransitive), from Old French relier "assemble, put together; fasten, attach, rally, oblige," from Latin religare "fasten, bind fast," from re-, intensive prefix (see re-), + ligare "to bind" (see ligament). Sense of "depend, trust" is from 1570s, perhaps via notion of "rally to, fall back on." Typically used with on, perhaps by influence of lie (v.2). Related: Relied; relying.