What is the meaning of idiosyncratic when refering to multiprocess abstractions? I am currently reading this paper on library operating systems, more specific on Graphene. I stumbled over the following sentence:

"Because multiprocess abstractions, such as signals or System V IPC, tend to be idiosyncratic, an essential problem is identifying a minimal, host-independent substrate upon which to implement OS-specific abstractions." (Page 3, design options paragraph)

But I don't understand what is meant by idiosyncratic multiprocess abstractions? What is the meaning of idiosyncratic in the context of multiprocess abstractions?
Let me rephrase your quote:


  Implementations of multiprocessing in various systems tend to be rather different. Each system uses its own peculiar "vocabulary". When we port each such system to new hardware, we need to code afresh the entire multiprocessing subsystem. One way to address this difficulty is to come up with a small set of multiprocessing primitives which, on the one hand, can be used to implement all the multiprocessing mechanisms in known systems, and on the other hand, is simple enough to code for each particular hardware. This will drastically reduce the effort required in porting operating systems.