Why did tree shaking as a phrase come to exist when “dead code elimination” had been around forever?
"Tree-shaking" refers to a whole-program analysis where you discard entire modules and functions if they are never invoked.
They are conceptually the same, but a compiler author will likely have to implement them separately, so having two names helps.
And I think with LTO it's all the same anyway (in the past there were a lot of gnarly details how the compiler/librarian actually created a static link library to avoid linking code that's not actually used, but that all doesn't matter anymore with LTO).
2) I was curious about which term actually came first.
The first use of "dead-code elimination" I could find was this 1973 dissertation: https://research-repository.st-andrews.ac.uk/bitstream/handl...
I couldn't find any use of the term "tree shaking" or "tree shaker" in the realm of computing on Google Scholar (it was all citrus tree or other arboreal topics, weird). The earliest discussion I could find with the word is this on comp.lang.lisp: https://groups.google.com/forum/#!topic/comp.lang.lisp/pspFr...