mildew: [OE] Mildew originally meant ‘honeydew’ (which is a sort of sticky substance exuded by aphids and similar insects on to leaves). It is a compound noun formed in the prehistoric Germanic period from *melith ‘honey’ (a relative of Latin mel ‘honey’, source of English mellifluous and molasses) and *daw-waz, ancestor of English dew. The metaphorical transference from ‘honey-dew’ to a less pleasant, fungal growth on plants, etc took place in the 14th century. => dew, mellifluous, molasses[mildew etymology, mildew origin, 英语词源]