Information & Library Science
- acronym forexplosive reactive armour (written as ERA)
Origin & History of “era”
In ancient Rome, small discs or tokens made of ‘brass’ (Latin aes, a descendant, like English ore (OE), of Indo-European *ajes) used for counting were known as area. In due course this developed the metaphorical meaning ‘number as a basis for calculation’, and from around the 5th century ad it came to be used in Spain, north Africa, and southern Gaul as a prefix for dates, some what analogous to modern English ad. By extension it was then applied to a ‘system of chronological notation, as dated from a particular event or point in time’, the sense in which English acquired the word. The more general ‘historical period’ is an 18th-century semantic development.