Chaya comes from a gypsi slang. In Germany explicit in Frankfurt/Main Chaya is another word for hot girl, bitch, etc... It is only used for women. Men are called chab or chabo instead, but this word can have different meanings, so search for the definition.
Chaya is meant to be a hot girl and thus often adopted by young girls referring to themselves.
Unfortunately it is an orthographic mistake, hence the word correctly spells Tschaia or Tschaie, which originates from a whole set of moving languages (Read gypsiy slang et al) and means plainly a girl.
Hence those languages are mostly spoken languages, it is usually hard to define the correct orthography, yet the transformation into chaya might be related to spanish (that certain latin(a/o) touch) or just shows the typical social lower class educational level.
* These videos are coming directly from Youtube, they may or may not be most relevant to the word "Chaya"
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