the.com/conspirator

means A person who secretly plots with others, usually to do something illegal or harmful.

from From Latin conspirare — 'to breathe together' (con- 'with' + spirare 'to breathe'). The image is striking: plotters huddled so close their breath literally mingles, in on the same secret. Latin used it both literally, for harmonious blending of sounds or voices, and figuratively, for being of one mind — which curdled into the sense of scheming in unison. It entered English through Old French conspirer in the medieval period, already carrying its shadowy, plotting sense.