What is the X in X-mas?
1680s, type of firework, from sky (n.) + rocket (n.2). The verb, in the figurative sense of "to rise abruptly and rapidly" (often with suggestion of 'and then explode and vanish'") is attested from 1895.
: the week's third skyjack to Cuba (1968+)
To take control of an aircraft illegally, usually by claiming to have a weapon or a bomb; commit air piracy (1961+)
[modeled on hijack]