coerce: [17] The underlying etymological meaning of coerce is ‘restraining’ or ‘confining’. It comes from the Latin compound verb coercēre ‘constrain’, which was formed from the prefix co- ‘together’ and the verb arcēre ‘shut up, ward off’ (possibly a relative of Latin arca ‘chest, box’, from which English gets ark). An earlier, 15th-century, form of the English word was coherce, which came via Old French cohercier. => ark
coerce (v.)
mid-15c., cohercen, from Middle French cohercer, from Latin coercere "to control, restrain, shut up together," from com- "together" (see co-) + arcere "to enclose, confine, contain, ward off," from PIE *ark- "to hold, contain, guard" (see arcane). Related: Coerced; coercing. No record of the word between late 15c. and mid-17c.; its reappearance 1650s is perhaps a back-formation from coercion.