How did the term "Sidejacking" come out? What is its origin?
The word is obviously derived from Hijack.
Presumably this word arises because the technique involves using "cookie" information from data transmitted unencrypted in conjunction with encrypted data. I would speculate that the word "side" was compounded with hijack because the encrypted and unencrypted data are metaphorically side by side.
SideJacking works only if the site catches a non-SSL cookie, so any Web site that uses SSL exclusively would be safe from SideJackers. SideJacking was first demonstrated by Robert Graham, CEO of Errata Security at Black Hat in 2007.