Thanks Fei, added to OP.
CG, when you think of it, the original English is pretty weird anyway.
Boot = heavy footware, is of course a contraction of "bootstrap" a joking reference to the task of starting up machines like the original house-sized Collosus used to break Enigma code messages in WW2, as being akin to lifting yourself in the air by pulling on your own bootstraps. (how do you run a program without an OS, or a BIOS or an eprom, just an enormous collection of inter-connected thermionic valves ?).
I suspect an American English influence on the term, or if it were English English, we'd probably be talking about shoe-laces not bootstraps, and the "shoe-disk".
Perhaps take-off cylinder is more to the point after all. (how about "launch point")