I was thinking recently about defunct currency names. I don't just mean defunct currencies, since the Zimbabwean dollar is a defunct currency, but the name 'dollar' lives on. Some defunct currencies do fit, since the Argentinian austral is now defunct, and so is the currency name 'austral'.
There are usually at least two parts to a currency; the unit and the subunit, e.g. dollar and cent. In some cases the name of a subunit becomes defunct. For instance, the Angolan kwanza was divided into 100 lwei. However, the lwei was replaced by the centimo in the 1990s, though the kwanza still exists.
In some cases, a defunct name is very close to an existing name. The Mozambicans had some coins minted in 1975, which were called meticas: there were 100 centimos to the metica. However, that currency did not survive, and it was replaced by a new one, in which there were 100 centavos to the metical. The plural of metical is meticais.
There are times when the name of a subunit seems to disappear from history. Modern African states have typically suffered from high inflation, so gradually the Ghanaian pesewa, a subunit of the cedi, and the Zambian ngwee, a subunit of the kwacha, disappeared. However, the pesewa re-emerged in 2007, after the Ghanaians revalued their currency. The Zambians will revalue their currency in January 2013, so coins denominated in the ngwee will once more be seen.
When the UK switched from a pre-decimal to a decimal system in 1971, the shilling disappeared - though the old shilling and two shilling coins still circulated until the early 1990s. And the shilling still survives in countries such as Kenya and Uganda, though really it is a different beast, since it is divided into 100 cents there, not 12 pence.