Preface: This is one of those questions that deals with personal convictions and preferences rather than a clear-cut Biblical statement. This actually came up not too long ago when our Pastor was preaching a sermon on the difference between the three.
A Biblical statement is simple. The Bible says "Thou shalt" or "thou shalt not". (Example: Theft - thou shalt not steal)
A Conviction (in his definition) is a position on a subject based on overwhelming Scriptural support, but no direct statement from Scripture. (not watching unwholesome movies based on "I shall set no evil thing before my eyes")
A preference is simply something we prefer. (short hair on men, wearing a tie to Church)
Often the line between conviction and preference is blurry. Many preferences can be loosely based on Scriptural understanding, and some convictions are based more on personal belief than the Word.
That said, I think the rest of this answer falls in that line between the two.
The Bible doesn't directly address "swear words" as we use the term. When the Bible has the word "swear", it is usually a translation of a word meaning "take an oath".
However, the Bible DOES say that what we say is important for many reasons. To list just the first two:
- The words we use can hurt others.
- The words that come out of our mouth reveal the condition of our heart and spirit.
Using just the second principle, if we are cursing, it's a sure sign that our spirit it not where it needs to be.
There's an entire sermon on the subject online here.
The relevant Bible section is James 3:1-11 (KJV)
My brethren, if any man offend not in word, the same is a perfect man,
able also to bridle the whole body.
Behold, we put bits in the horses’ mouths, that they may obey us; and
we turn about their whole body.
Behold also the ships, which though they be so great, and are driven
of fierce winds, yet are they turned about with a very small helm,
whithersoever the pilot listeth.
Even so the tongue is a little member, and boasteth great things.
Behold, how great a matter a little fire kindleth!
And the tongue is a fire, a world of iniquity: so is the tongue among
our members, that it defileth the whole body, and setteth on fire the
course of nature; and it is set on fire of Gehenna.
Every kind of beasts, birds, things of the sea, is tamed ... But the
tongue can no man tame; it is an unruly evil, full of deadly poison.
With it we bless God, even the Father; and with it we curse men, which
are made after the similitude of God.
Out of the same mouth proceedeth blessing and cursing. My brethren,
these things ought not so to be.
Doth a fountain send forth at the same place sweet water and bitter?
Can the fig tree, my brethren, bear olives? Or a vine, figs? so can
no fountain both yield salt water and fresh.
Also, Matthew 15:18-20 (KJV)
But those things which proceed out of the mouth come forth from the
heart; and they defile the man.
For out of the heart proceed evil thoughts, murders, adulteries,
fornications, thefts, false witness, blasphemies:
These are the things which defile a man: but to eat with unwashen
hands defileth not a man.
For me, the final test comes down to "what is the frame of mind I must be in if I'm saying this particular word/phrase".
There is no situation where a loving heart shouts or mutters things like "what the ######## are you doing, you ########. Learn to drive the ######## car!"
In any sentence where I can consider using what we would call "swear" words, I need to be either angry, disrespectful, reacting to a sudden injury or fright, or a combination of the above.
In none of those situations am I being "godly" or "Christ-like" which should be the goal of every Christian.