Thank you for that contribution Jean, you have now opened a door I tried to get somebody to open with an earlier posting, but it seems I was just a little too obscure for those who follow this Forum.
As you so correctly indicate, the wrongko shown in the Candi Sukuh bas-relief is an ancestor of the style now known in Jawa as "Sandang Walikat", in English this translates as:- "sandhang" = "clothing", "walikat" = "shoulder blade/scapula" (usually incorrectly given as "rib"). So in modern Jawa the scabbards of this type are likened to the human shoulder blade, yes, there is a small similarity. There is a lot of Islamic influence in Javanese language and society.
But what were they called in Old Javanese?
Well, Zoetmulder doesn't tell us, so we need to go to a language that still has some large similarity to Javanese before it was subjected to Islamic influence, and that language is Balinese, not only is the language similar, but modern Balinese people who are not indigenous Balinese, but who have descended from the Javanese immigrants of earlier times refer to themselves as "Wong Mojopahit" = "Mojopahit People".
So, what is the Javanese sandang walikat dress called in Bali?
The name is "Kajongan".
The word "kajongan" is from the root "jong", and jong means "boat". The word "jong" appears in Modern Javanese also, where it has the same meaning "boat". It has the alternative pronunciation in Javanese of "jung". The word "jong" became a loan word in Chinese, where it became "junk", but the Javanese, who in olden times were perhaps the world's greatest seafarers were moving all over the southern oceans of the world long before the Chinese began to use the sea as a highway.
The word "jong" also appears in Old Javanese, where it also means "boat".
In both Old Javanese and Modern Javanese "jong" also has the meaning of "umbrella", and it is not too much of a stretch of imagination to understand why that is so.
However, we're talking about keris scabbards, not things to shade us from sun.
When we place "ka" in front of "jong" and "an" after "jong", we create the word "kajongan" = "boatlike".
So when we refer to this particular type of keris scabbard we are in fact saying that it has a shape like a boat, it is "boatlike". This becomes even more apparent when we see this boat-like form with a hilt carved as an ancestor figure, or a guardian figure, projecting above it. That figure is riding along in the boat.
It is clear that the scabbard form developed because of the need to accommodate the asymmetric form of the keris itself, and the need to retain it in a waist sash, and when we see an early interpretation of that form, as in the Sukuh relief representation, we can understand exactly why it was named as "boatlike".
But maybe not all of us can see the similarity between the early kajongan scabbard and an early Javanese boat? Perhaps the pictures below will clarify that.
But the relationship between keris scabbards and boats does not stop here.
A bugis form of scabbard has the name "jong-jonga". Now, according to Ahmad Ubbe this translates from Bugis language to Indonesian as "gerbang-gerbangan" = "it looks like a gate"/"gate-like". I reckon they must have pretty queer sort of gates in Sulawesi. However, he goes on to say that some people refer to this shape as "lopi-lopi", which he gives in Indonesian as "perahu-perahuan" = "it looks like a boat"/"boat-like".
So now we have Bugis people referring to a type of keris scabbard as "boat-like", Balinese people referring to a type of keris scabbard as boat-like. The Bugis people were probably the first people outside of Jawa/Bali to adopt the keris, it seems reasonable to me to assume that they also adopted the scabbard name "kajongan" which over time transformed into "jong-jongan", which in Bugis language means "gate-like". But some Bugis people understood the "kajongan" meaning, and that became "lopi-lopi" = "boatlike".
See here and scroll down to post #17:-
not Bugis influenced, but rather the other way around.
As I said, Zoetmulder does not give us "kajongan", but I'd bet my shirt on it that this scabbard style that we can see at Candi Sukuh was named "kajongan" in Mojopahit Jawa, just as it is named the same way in Bali and Sulawesi.
This, of course, destroys that silly old European generated myth that the Javanese designed the modern Central Javanese ladrangan in honour of their ancestors who travelled to Jawa in boats. Yes, this boat relationship does have a foundation, but it grew in the wrong direction. When we can strip away all the silliness that surrounds the keris we might begin to understand what we are really dealing with.
Anyway, here are some images that might make the whole thing a little more clear.
I don't think the images need explanation, except the bas-relief, which is the famous Borobudur ship. This is what Javanese ships looked like back around 900CE.