How are Indonesian nicknames formed? When and how do people use nicknames?

As for Ahok, this nickname is derived from Hakka (阿勰). A common format for nicknames derived from Chinese would be A Xxx (A Hok, A Tjong, A Fie, etc), sometimes also written as Ah Hok. Actually many of the Chinese also have nicknames based on their Indonesian name, which are derived more or less as explained below by . Among very close friends, sometimes the differentiator between people having the same name might be a certain physical feature. Note again, only among very close friends do we use this kind of differentiator (plump, skinny, curly hair, etc)

We Indonesians like making abbreviations. So Jokowi = Joko + Wi (from Widodo). 'Ahok' I guess comes from his Chinese name. Prabowo has been referred to as 'Om Wowo', Susilo Bambang Yudhoyono is SBY (pronounced 'Ass-Bay-Yay'). No pun intended! But there is no strict 'rule' in making nicknames, it's just what rolls off your tongue the easiest.

The safest way to know the answer is asking the person directly. Because not even native Indonesians can always be sure about it. By default, the first word of the name is a safe guess, with a few narrow exceptions (for example, someone whose name's first word is "Muhammad" is unlikely to be called "Muhammad" in their daily life). Some common names have their associated common nickname. *citing from Aditya -> Adit Taufiq -> Opik *and these are from me Yusuf -> Ucup Rizki -> Kiki Abdul -> Bedul In general, there will be some correspondence between the pronunciation of the nickname and the pronunciation of the proper name. But it's not always the case. For example, Basuki Tjahaja Purnama's nickname is Ahok. I would guess that "Ahok" word is derived from his proper Chinese name. Anyway, the rule of naming in Indonesia is very liberal. So it's always good to ask to the person directly.

Hmm.. i might be wrong, but i'm sure everyone have nicknames, although not everyone use it in public/in formal occasions. i have a javanese friend named Benedictus Prabani Indrawahyu Darpito, with Beni as a nickname. teochew-chinese friend named Novianus nicknamed Asun, Michael nicknamed eki, Heldi nicknamed dedy, Dennis named kodek, Niece named Twensylia nicknamed Wewen, Co-worker named Sophie nicknamed Atun, sister's friend named Hesty also nicknamed Atun. Our first President, Soekarno/Sukarno was born as Koesno Soesrodihardjo. Current Presidet, Susilo Bambang Yudhoyono, his name was abbreviated as SBY. Soeharto's daughter, Siti Hediati Hariyadi was known as Titiek Soeharto and his brother, Hutomo Mandala Putra was known as Tommy Soeharto too. Ahok derived from his Hakka name. I'm sure Prabowo Subianto also have his nickname (probably his child-name) For me, i was called Aiu, derived from my Teochew-chinese name 陈学友 nicknames here are freely given, some are abbreviations of their full name, some derives from their chinese name, their habits, their name since children, what/who they are known for etc. I don't think there are any formats for nicknaming, and nicknames are usually used in non-formal occasions. We address each other based on age. Calling older people by name is considered impolite. If the name is unknown, use formal address by their estimating their age. If thy are much older, address them with Bu, Ibu, Tante, for females and Pak, Bapak, Paman, Om. If they are slightly older, Kakak, Kak, Ecik, Cik, Mbak for females, abang, bang, akang, kang, mas, ko, etc. if they're fairly younger, addres them as adik, dik, adek, dek regardless of gender.

I don't think there is any systematic rule how the nicknames come and when it is used. In social context, you learn somebody's name when he introduces himself to you or you heard him from other people, so you will address them with this name. You appear to be westerner, an important point to note is that unlike Western names, there isn't normally a given name/family name distinction for most Indonesians, so there isn't distinction where you would call someone "Adam" in informal situation but "Mr Leigh" in formal situation. For example, my family calls me "Danil" (a portion of my first name, presumably because it's easier than a 3 syllable name for everyday purpose) and during school that's the name I give people when I introduce myself. Some people might call me Hamdanil, probably because they prefer that name, or because they don't know I go by Danil, but which name they call me does not depend on the situation or closeness of the relationship (well, maybe close friends are less likely to call me Hamdanil, but that's just because they have higher probability of knowing my childhood name, not because any norm dictates that). I would say the default is someone go by their first name, but they have higher likelyhood of having a short name or nickname if : they first name is long (like me) they first name is common (e.g. Jokowi). Another example, "Muhammad" and "Siti" is a very common first name, most of people so named go by their second name. Their name is of foreign origin or something like that, that doesn't go nicely with Indonesian phonology. They like the short name or the non-first name better (many of my friends are like this, they just introduce themselves with their second name, short name or whatever), and people will address them with this name.

Well, only if the nickname is widely used and sounds catchy, it may be used. Prabowo Subianto, if you follow nicknaming pattern like Jokowi, it would be Wosubi. It doesnt sounds good anyway. There is no definite pattern for defining nick name actually.   Susilo Bambang Yudhoyono used SBY as his nickname anyways.