Why is the word used?
I think this is a good discussion of the topic - I tend to favor the "argument" that the word came from mathematics, as in "argument to a function":
https://english.stackexchange.com/questions/144141/what-is-the-sense-of-using-word-argument-for-inputs-of-a-function
Is it only used in Java programs?
No. But Java is the only language I know of where args is required to execute main program function.
People often speak of command line arguments. Java was built using C/C++, which uses args
Why can't another word resembling it be used instead?
Depending on the context, people might substitute "parameter" or "switches," but within a language like Java, arguments is considered correct.
You would be surprised how a word can take hold in programming, and continue to be used outside its original context. The original hackers at MIT used the term "foo" in a pretty specific context, and "foo" soon became the prototypical function that programming manuals and books used as their example when describing how functions operate.
Speaking of "functions" - one language might call it a "function," and another language might call it a "method."
See also: https://en.wikipedia.org/wiki/List_of_computer_term_etymologies
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