trichloromethyl chloroformate [trahy-klawr-oh-meth-uh l klawr-uh-fawr-mit, -meyt; trahy-klohr-oh-meth-uh l klohr-uh-fawr-mit, -meyt] Word Origin noun Chemistry. diphosgene. Origin of trichloromethyl chloroformate tri- + chloro-2 + methyl