Other forms: pests
A pest is an animal or insect that damages crops or property. Aphids, rats, slugs, moths in a wardrobe.
The word is entirely about the damage rather than the creature, so the same animal is a pest in a barn and wildlife in a wood. Pest control is a real trade and integrated pest management is the modern approach. There is a mild everyday sense for people, since calling a child a little pest means they are being a nuisance, and that is affectionate. The word comes from the same root as pestilence.
Latin
pestis
Middle French
peste — pestilence
English, today
pest
In the 16th century in the sense of "pestilence" and specifically bubonic plague from Middle French peste (“pestilence”) (whence French peste). The other meanings are recorded soon after. Ultimately from Latin pestis.
Etymology from Wiktionary, CC BY-SA