What's old is new... Unikernels are quite reminiscent of the VAXELN product from ~30 years ago; write the application code, link in the various services you need, and disk or network or ROM boot the results:
It was less "reinvention" and more "making them actually useful." From the ACM announcement[1]:
Although the concept of virtualization was first explored in the 1960s in the context of mainframe computers, it languished until Mendel Rosenblum and his students at Stanford University rediscovered the idea as a simulation tool for new multiprocessor architectures.
It goes on to point out how they created a vibrant industry and research area around the technology and spurred a shift to virtual-machine-based architectures.
Eh, most of the fun of alt.folklore.computers is listening to a bunch of geeks who were there from the time CTSS seemed like a novel idea moan about how everything was done before, either by DEC in the 1970s or IBM in the 1960s (or 1950s!). Oh, and DEC, not Digital: The VAX was an abomination and command line technology peaked with TOPS-20, if not TOPS-10.
(Seriously. One of the people I quoted claimed elsewhere, without any hint of irony, that IBM invented personal computing by putting CP-40 on System/360 mainframes, to give everyone their own personal guest system on the shared hardware. Yes, and the Ancient Romans invented radio by reflecting sunlight with mirrors; after all, it's all EM radiation!)
Or processes. If your hypervisor is KVM, then your KVM + unikernel essentially is a Unix process running on the host, just using a rather complex API instead of syscalls.
Of course in many ways "cloud" computing is just another implementation of a 370/VM mainframe system. I find the evolution fascinating. Oh and I had a comms processor (terminal server to a modem bank) which turned out to just be a MicroVAX 3 runing VAXELN. The CPU was some what "cut down" (I think optimized was the word they used) to make it more cost effective. VMS would not boot on it.
https://news.ycombinator.com/item?id=9259292
Or Service Virtual Machines: http://alt.folklore.computers.narkive.com/LXzjsdU7/was-vm-ev...
Or Exokernels: http://pdos.csail.mit.edu/exo.html