As I read at http://en.wiktionary.org/wiki/kidnap, the etymology for kidnap is
kid (“child”) + nap (“nab, grab”)
Can an adult person also be kidnapped? Would it sound funny to say so? The definition mentions person, not child, but I'm not sure. (In my language we have a borrowed word kidnapper, but I only heard it referring to someone who abducted children or house pets, probably because the users of the word recognised the kid stem in it.)
Best Answer
It is normal to use "kidnap" in a non-child context. It does not sound strange at all, and it is actually the correct legal term for the crime, which is not specific to children:
"Abducting" is a common synonym for "kidnapping".
Sometimes the "kid" in "kidnapping" is replaced by some other noun, as in "dognapping". This is often used seriously (as dognapping is) but may be slightly humorous in more bizarre or trivial circumstances, like pignapping or lappynapping.