The prime minister recently indicated that even after 19 July, trumpeted as Covid freedom day, we might still need to follow some “precautions”. A cynic might suppose that this term is now being used only so that the government can say that it lifted its “restrictions”, or what were vaguely termed “measures”. Otherwise, what’s the difference?

In Latin, praecautio means circumspection or wariness, deriving ultimately from cavere, to take care. (Which is where we also get “caveat emptor”.) Its first recorded use in English is by the diplomat Sir Henry Wotton, writing from Dublin to the poet John Donne in 1599. Wotton recommends to Donne a certain “gentleman of Germany” who might be helped with a sum of money after “due precaution” taken to ensure his deservingness. Much later, “precautions” became a 20th-century euphemism for birth control.

Perhaps most plague-relevantly, philosophers and lawyers talk of a “precautionary principle”, which says that in the face of a risk that would have extremely bad effects if it came to pass, one should err on the side of caution. Oddly, though he urges precautions now, this does not seem to be a thought that has ever previously occurred to Boris Johnson.

• Steven Poole’s A Word for Every Day of the Year is published by Quercus.