[A. G. Maisey]

Jaga, I do not yet have any solid answers to give you. I asked questions in the hope that somebody might carry out some serious research and also have the time to think. The simple truth is that I have too many irons in the fire and cannot give all the questions that are spinning in my mind adequate attention.

The questions are there to generate ideas. Just that.

However, I might be able to move just a little further on a couple of points.

The "balu makabunbun" idea seems to me to be something that might have come after the event, that is, the figure was created, and when it was created the creator had a clear idea in his mind in respect of what he had created, however, some time after the creation this figure was described by someone as "balu makabunbun". But why choose a widow? Why not just a woman?

However, if we start with the idea of "a widow", we have the phrase "balu makabun", and that name does not relate in even the slightest degree to the form of this figure, that name is not a description, it tells us something that we cannot see just by looking at the figure:- a widow is involved.

We can clearly see that this figure is female. What we cannot know without the name is that it is a widow, not only a widow, but a widow who has lost her husband and is left with daughters. So then the question becomes:- "which widow"? Well, it cannot be Durga, because Durga is not married, never having had a husband, she had none to lose. Some people regard her as the "eternal virgin", but then, how can that be when she had four children? These were her spiritual children:- Ganesha, Kartikeya, Saraswati & Lakshmi. So if this hilt form is truly named as a widow, ie "balu", it most certainly cannot be Durga.

The function of a keris hilt is to protect the shrine that is the keris, so whatever widow this might be, she is fulfilling a protective function.

How many candidates are there?

It seems that we need a widow who has daughters.

Durga is an incarnation of Parvati, as is also Kali, Parvati is the sakti (energy/power ) of Siwa. When Siwa is calm the sakti is Parvati, when Siwa is angry the sakti is Durga, when Siwa is ferocious the sakti is Kali. Siwa is empowered to exercise the particular aspect of Himself through his sakti. In Tantric rituals it is possible for Durga and Kali to become mixed.
In Jawa Durga was worshipped primarily as a protective goddess and the principal goddess of Saivism (the worship of Siwa), she is also the goddess of fertility, and this aspect overlaps the pre-Hindu goddess of fertility, Dewi Sri.

The relationship between the Jawa/Bali folk character Calon Arang & Durga is that Calon Arang worshipped Durga with performance of the Tantric marana ritual, performance of this ritual gives the worshipper the powers of the god worshipped. One of Durga's powers is the ability to spread disease, this was the power that Calon Arang wanted in order to punish the people of Erlanga's kingdom for being afraid to marry her daughter. So at this point, when Calon Arang gained Durga's power to spread disease many simple people were confused as to just who was responsible, was it Calon Arang, or was it Durga? Over time the two merged, but only in uneducated popular belief.

Durga was not a widow left with daughters, but Calon Arang gained her powers and Calon Arang was a widow with a daughter.

Rangda is an incarnation of Calon Arang. The meaning of the word "rangda" is "widow". In Bali many people believe that Rangda can exercise a protective function. To understand this we need to recognise that good & evil are present in all creation, evil occurs when the balance turns in that direction.

To my mind Calon Arang seems to fit into the Balu Makabun frame pretty nicely:- widow + daughter. But maybe it is really Calon Arang after she has gained the powers of Durga and as her Rangda incarnation. Never Durga, but an aspect of Durga present in Calon Arang and incarnated as Rangda.

Why is the hilt figure's head covered, or veiled? Perhaps because Calon Arang --- or Rangda --- has gained the powers of Durga, but she is not Durga:- the powers are there, but who is wielding them?

Then we have Queen Mahendradatta.

The above is just a rough sketch of the ground that we have to work with. I have covered it with hypotheticals, as I have said, I have no answers, only ideas and questions.
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Durga in Jawa between tenth century & fifteenth century. Within the courts mainline Hindu belief was followed with Durga in a protective persona and as the slayer of the asura Mahisasura. Those outside the courts, the lay people, understood Durga as a raksasi. People who study this sort of thing tend to believe that this erroneous understanding was generated by lack of knowledge of the Tantric rituals engaged in by the elites.
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Confusion. The balu makabun/mekabun/mekebon/mekebun confusion probably arises from two sources, in Balinese formal speech the pronunciation of "makabun" is with a distinct "a", in colloquial speech the "a" becomes an "e", even though the word itself does not alter. A person who is not a native speaker of Balinese would note the word in accordance with what he hears, if that person is not Balinese it would be natural to understand the "kabun" --- which spoken colloquially will sound like "kebun" or even "kebon" --- as "garden", and he will construct his understanding based upon this. So, we get the "widow in a garden" idea.
It is I believe a construction from outside of Bali.
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Iconography. As to what this female hilt style represents, I doubt that we will ever really know. Perhaps a few thoughtful hypotheses might open an avenue of thought that could result in a defensible interpretation of the form.