[A. G. Maisey]

Throughout Indonesia, the more general word for the keris scabbard is "sarung", which is the traditional garment used by men and women to cover the lower body, actually just a length of cloth that is wound around the body for women, or a tube of cloth for a man. The use of this word for the keris scabbard is an indication of the philosophical relationship between the keris and a man.

The word "sarung" is correct usage in Bahasa Indonesia, the word "wrangka" is correct usage in Javanese.

In Jawa the word used by the vast bulk of keris conscious people is "wrangka", in Javanese the "a" in this word is pronounced as an "o", but the sound is made in the back of the throat, not the front, so the usual way we write the word is "wrongko", as David has advised.

In old publications we see the "a" in this word with a small dot over it, indicating the pronunciation, but with modern typewriters this dot was unable to be applied, so just the "a" was used, and the only way in which to know the pronunciation was to be able to speak the language.

The general population of Jawa, especially those people of later generations and those who are not keris conscious still seem to mostly use "sarung", rather than "wrangka".

The dictionary correct version of "wrangka" is "warangka", however the spellings "wrangka" and "rangka" are also listed in most Javanese dictionaries.
In my experience, the only time I have heard the pronunciation "warangka" is in a situation where somebody is trying to impress somebody else with his status or erudition.

The word "wrangka" correctly refers to the entire scabbard, including the gandar, but it is used loosely to refer to only the top section of the scabbard also. The top section of the scabbard is correctly named as the "gambar" (this word also means "picture"), but most of the craftsmen who actually make these scabbards call it the "atasan", which simply means "top".

The words "warangka" and "wrangka" appear in Old Javanese, and in this language they have the alternate meaning of an enclosure in which to keep livestock --- stable, yard, coop --- or a nest. Colloquially the word can also imply a prison.

A derivative of the word "wrangka" in Modern Javanese is "wrangkaning ratu", which can be loosely translated as "the ruler's protection", which in turn equates to the rank of patih, which can be understood as the ruler's chief councillor, or vice-regent, or prime minister; this usage does not seem to appear in Old Javanese, whilst the word "wrangka" for "scabbard" does appear, thus the usage associated with a court comes from the usage associated with a keris, not the other way around. Again a philosophical association between the keris and a man, in this case a ruler, is shown.

The lower part of the keris scabbard is named the "gandar", the alternate meaning of "gandar" is "something that forms a fine/good straight line", so here gandar is simply a description that through common usage has become a name, The word "gandar" does not seem to appear in Old Javanese.

The above is only a very brief and simplified explanation of the keris scabbard, when we get into the names of the various characteristics/parts/sections of the scabbard it gets considerably more complex.