Every language, like a living organism, develops and evolves over time. In any case, if this language is actively used. New words appear in speech, old ones disappear, but most importantly, the meaning of actively used ones is constantly changing. In the Russian language, there are many words that have changed or distorted their original meaning. Among them there are those who have become abusive today, although they did not mean anything like that before.
Word "mug" - originally this word in Russia was called terrible masks. Gradually, the meaning of the word changed, and it began to be used to refer to a person with an unattractive appearance, in particular with an ugly face.
Word "Pentyuh" - in ancient times, this word meant only the stomach. Gradually, it began to be applied to very lazy, idle people who do nothing but eat and sleep.
Word "Bitch" - originally this word meant not at all what it means today. Moreover, he was not used as an insult. In ancient times, the dead body of a dead animal, dead cattle, carrion was called a bitch.
Word "Bastard" - once this word was not applied to people at all. The ancestors called the scum a sediment that fell to the bottom of a vessel from some turbid liquid.
Word "Idiot" - the original meaning of this word was also not offensive. Moreover, the word was applied not to people, but to objects. They called them a stump of a tree, an idol, a block.
Word "Beast" apparently migrated to the Russian language from German. For a long time it did not carry a negative connotation and meant wealth or money. Gradually it began to be applied to pets and only then as an insult.
Word "scoundrel" initially had no negative connotation. It became obscene only at the turn of the 18th century. Prior to this, this word was called simple, low-born people, representatives of the people.
Word "Boob" - in ancient times it was also not abusive. At one time it meant only a shepherd.
Word "Mymra" - in ancient times, all those who constantly stayed at home and did not climb out were called mymrs. There was even a derivative verb: "mumrit" - to stay at home without getting out.
If you want to know even more interesting things, then you should read about who are the "spitters", what they did in Russia and why they were held in high esteem.