deteriorate: [16] The meaning of deteriorate resides etymologically in its first syllable, which represents the Latin preposition dē ‘down’. To this was added the adjectival suffix -ter, to produce *dēter ‘bad’, and this in turn was modified with the comparative suffix -ior to dēterior ‘worse’. Dēterior formed the basis of the verb dēteriorāre ‘get worse’, source of English deteriorate. [deteriorate etymology, deteriorate origin, 英语词源]