Where does the word “delirium” come from and What does delirium mean?

The ancients employed figures of speech just as we do.

Thus, if a person in the days of Caesar wished to say that another was suffering from vertigo or was wandering in mind or speech, he might use the Latin verb deliro.

The literal meaning was “to stray from the furrow,” lira being “furrow.”

Naturally, no farmer in his senses would deliberately turn his oxen aside from the furrow previously plowed or the row that he was harrowing, and the term therefore came to be applied to anyone not in his senses, to a person suffering from a disordered mind.