Echinochloa is derived from echinus meaning hedge-hog and chloa means grass. Frumentacea is derived from frumentum means produce, especially of the various kinds of cereals, hence corn, grain.
According to the Rules of ICBN the names of the families should end in -aceae. Thus the new name for the family Gramineae became Poaceae. However, the name Gramineae is also exempted and conserved under 'NominaConservanda' because of their constant use for a long time.