referendum (n.)

1847, "a submitting of a question to the voters as a whole" (originally chiefly in reference to Switzerland), from French or German, from Latin referendum "that which must be referred," literally "thing brought back," neuter gerundive of referre "to bring or take back" (see refer). Fowler prefers a plural referendums because referenda is "too suggestive (cf. memoranda, agenda &c.) of the correct sense--questions to be referred."