Maybe the original users of the words were so ignorant anything over four letters was beyond their vocabulary. Things do not seem to have changed a lot

Easier to say I guess. (or at least easier to have slip out of your mouth at the wrong time.)

Because the people who use them in everyday speech can't use big words.

dumb people who say them dont know more than a few letters from the alphabet...der

Is four letters bad or something?

Last time I checked "eenie meenie chilli beanie", "ooga booga" and "I curse thee with warts" had more than 4 letters.

short, sharp and sweet is the way to go!

English is a Germanic language, specifically a descendant of Anglo-Saxon. However, english vocabulary is a mix of Latin words and anglo-saxon ones, due to the Norman Invasion in 1066. The Latin based words tend to be the vocabulary of the upper levels of language: arts, culture, government, history, medicine, science. Anglo-Saxon based words form the bottom layer ie everyday things. It is a known fact that when an english speaker wants to make the most emotional statements, he resorts to Anglo-Saxon words of one syllable: we can see this in shakespeare's Richard II This royal throne of kings, this sceptred isle, This earth of majesty, this seat of Mars, This other Eden, demi-paradise, This fortress built by Nature for herself Against infection and the hand of war, This happy breed of men, this little world, This precious stone set in the silver sea, Which serves it in the office of a wall Or as a moat defensive to a house, Against the envy of less happier lands,— This blessed plot, this earth, this realm, this England. and in Churchill's WW2 speech:We shall go on to the end, we shall fight in France, we shall fight on the seas and oceans, we shall fight with growing confidence and growing strength in the air, we shall defend our Island, whatever the cost may be, we shall fight on the beaches, we shall fight on the landing grounds, we shall fight in the fields and in the streets, we shall fight in the hills; we shall never surrender, and even if, which I do not for a moment believe, this Island or a large part of it were subjugated and starving, then our Empire beyond the seas, armed and guarded by the British Fleet, would carry on the struggle, until, in God's good time, the New World, with all its power and might, steps forth to the rescue and the liberation of the old." Both of these are dominated by words of anglo-Saxon origin. So what has this to do with curse words/swearing? Clearly, swearing is another example of emotional speech, and as such would use words of Anglo-Saxon origin, and as short as possible. But the f word the s word and the c word are all A-S in origin.

Simple and fast to grab on to

Short, sweet and easy to remember. My three favorite things for a word to be.

One thing to consider is linguistics -- most swear words have an Anglo-Saxon/Germanic base. These languages (actually, Latin does it, too) tend to use short bases (one syllable) and combine them to create longer, more specific words (You have fire in one place which becomes the fireplace). If short bases express the sentiment, there is no need to lengthen them. Since English usually has one vowel sound per syllable, the length of such words are self-limiting. So there is frequently either a silent letter (the 'n' in d*mn) or two letters producing a single sound (the 'sh' in sh*t, the 'ck' in f*ck). Part of it is also the force with which one can spit out one of these words. They may only consist of three or four sounds, but most contain at least one hard letter, what linguists call a 'stop', such as 't', 'c'/'k', 'p' or 'b' (there are others). These letters, said as part of a word, produce a small puff of air that gives them added force, which is satisfying if you're using the word to express anger or frustration -- as they often are. The fact that anger, frustration, surprise and pain are frequently the impetus for using swear words also may influence their length. Swear words can usually be uttered in roughly the same length of time as would be required to emit a short yell. They express the user's initial reaction and, assuming the user is not alone, draw the attention of others. If I drop something on my foot, "excrement" takes too long to say. Try it yourself. Say "refuse" or "excrement" in the same sort of tone you might swear in, then try a common swear word. Or try a three-sound word with stops in it that isn't a swear word (e.g. cat, bot, tap). See which one draws attention the fastest.