pest

pest comes from Latin pestis, which did not mean an annoying insect — it meant a plague, a deadly epidemic, a curse, even ruin itself. To a Roman, a pestis was the worst thing that could sweep through a city. That weight of meaning explains the whole family.

The direct line keeps the disease sense:

- pestis → pestilence: a devastating epidemic, the kind that empties towns.
- pestilence → pestilent / pestilential: 'plague-like,' deadly, or harmful to body or morals.

Then the meaning softened over the centuries. The same word that named the Black Death came to name any creature that ruins crops or homes — a pest. From there:

- pest + -i- + cide (killer) → pesticide: a chemical that kills pests, part of the modern -cide product family (herbicide, insecticide, fungicide).
- And the verb pester, which now just means to annoy persistently, as if someone were a small plague buzzing around you.

That is the arc to remember: pestis started as mass death and slowly shrank — from plague, to harmful creature, to mere nuisance. The Hungarian capital Budapest and the German word for plague (Pest) preserve the old gravity; everyday English mostly keeps the lightweight end, where a pest is a mosquito or a nagging child.

A caution: pester is sometimes traced instead to Old French empestrer ('to hobble an animal, entangle'), with pestis only reinforcing it later. So treat pester as a probable but not certain member — the 'annoying' sense fits, but its roots may be tangled with a different word.