Arcadeep

It is still used to refer to things like fire retardant. To retard (pronounced ruh-tard and not ree-tard) means to slow or restrict the progress of something such as spoilage or fire spreading and is still a word with ligitimate uses, with the outdated ‘medical’ usage being a reference to a mentally disabled person’s slower mental progress.

I would imagine most people’s opinions on their own opinions are that they are correct