Indonesia is rich with languages. The national language itself, Bahasa Indonesia, is a conglomeration of over a dozen languages. As in every language, new words and slang terms are rife.
Many Indonesian slang words are simply shortened versions of the original, eg. tahu (know) into tau, habis (depleted) into abis. Many slang words, as well as proper words, are taken directly from another language, eg. sori (sorry), pren (friend).
Regional variations abound, and a person from Jakarta, who speaks Batawi, will not understand a person from Semarang when they say ‘Piye, jal?’ (How about it?), or when a person from Surabaya says they are Gacoran (A Big Mouth).
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Trends come and go in every country. Back in the mid 80’s in California, everything was ‘Rad’ (radical), which changed overtime to ‘Sick’, ‘Fat’ and many other things. What tickles me is the local use of certain expressions, that give an incling to the stuff that is around. Alternatively its fun to see nonsensical expressions, such as in the city of Bandung, in west Java. One distinct characteristic in Bandung slang grammar is generous insertion of the word ‘anjing’ in a sentence. The word means dog, but its usage in Bandung slang is merely for emphasis and not as a swearword, eg. ‘Nasi goreng Jalan Madura ngeunah pisan, anjing!’ which means ‘Fried rice in Madura Street is really delicious, gosh!’
Here’s Wikipedia’s page on Indonesian slang. You might try learning a couple of polite slang terms to have fun with, next time you visit Indonesia.