swearing, cursing, and saying bad words

[cbooth at ES.COM]

The recent discussion of the 10 commandments set me to thinking that
sometime in the history of English there might have been a semantic
extension of swear in the sense of "make an oath" to encompass "say a bad
(taboo) word." I think we can still swear oaths, as in "swear (on the bible)
to tell the truth" or "I swear to God I'm gonna . . ." and the like.
Swearing in this sense seems to involve the invocation of some sort of holy
object-bible, God, mother's grave, . . .
A curse, on the other hand, might or might not directly invoke a deity: "God
damn you to hell!" or "May you rot in the hell you so richly deserve" or "A
plague on both your houses."
These days both swear and curse also mean "say a bad word." Maybe "Goddamn
you!" and "Fuck you!" aren't that far apart, cursewise, but saying "shit" as
an expletive or calling someone a son of a bitch or using (if anyone
actually ever did) the old generic theatrical chestnut "Curses! Foiled
again!" seem not at all like swearing or cursing in the senses above.
So the questions I have are:
Was there a shift in the senses of swear and curse to include "say bad
words," or did they always encompass both meanings in English?
"Swearing" and "making oaths" seem to be based in the law-but wasn't there a
time in the history of English when there was essentially no practical
difference between legal and religious life?
What were the bad words in English in, say, 1066, or 1588, or 1611?
What about swearing, cursing, and saying bad words in other
languages-French, Arabic, or Hindi, for example.
What impact did the injunction against using the LORD's name in vain (Exodus
20.7) in the King James version of the bible have on the sociolinguistics
and history of English? (I don't think we should underestimate the influence
of the KJV on English, but it was based in large part on older versions, and
there were English vernacular versions of the bible at least as early as the
mid 1300s. Maybe priests even told people what the 10 commandments were in
English long before that. I believe, although I'm not a scholar of Hebrew or
a theologian, that in the KJV, LORD is printed in small caps as a euphemism
for the tetragrammaton YHWH, unutterable by Jews and apparently not even
printable by the C of E.)
In the end, it strikes me that in this note I might really just be asking
big questions about the power of words.
Curtis