you might think speculative execution refers to the policy of using drones to kill potential threats
or
it's an investment banking term related to loosing your financial life due to risky investments
but
it really is a performance tactic used in computer processors that created quite possibly the biggest security bug ever
the phrase just refers to doing something (execution) because it may (but probably not - speculative) be useful at some point in the future
it certainly seems to be of the zeitgeist, so much in this profit-seeking, competitive global marketplace that we inhabit can be attributed to this impulse to do things (anything) even if they don't turn out being useful
in Umberto Eco's 'Ur-Fascism', he refers to a very similar concept:
The cult of action for action’s sake. “Action being beautiful in itself, it must be taken before, or without, any previous reflection. Thinking is a form of emasculation.”
this basically means considering what to do before just going ahead and doing it is not efficient or hinders performance, which is pretty much exactly why Speculative Execution is included in the vast majority of computer processors today