You are right, SAYA was from the word SAHAYA, means SLAVE.
The old days, when we speak to people of a very high ranking or to a king, we have to call ourself with SAHAYA.
Then, in Bahasa Melayu (Indonesian) we shorten it became SAYA.
The same with the words SAHAJA -- > SAJA and BAHARU ---> BARU and DAHULU --> DULU.
All the best,
Ajiek Stoneman, Tokyo
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Doesn't "saya" have an etymology of meaning "slave" or "servant", the same way the "abdi" can mean "servant" or "I" in Javanese?
In Malay, they often just use "I" instead of "saya". One could probably get away with that in Indonesia; but I haven't tried it, yet.