The reverse process to amelioration is called pejoration or degradation. It involves a lowering in social scale connected with the appearance of a derogatory and scornful emotive tone reflecting the disdain of the upper classes toward the low ones.

Knave meant at first "boy", then "servant", and finally became a term of abuse and scorn.

Another example of the same kind is blackguard. In the lord's retinue of Middle Ages served among others the guard of iron pots and other kitchen utensil, black with soot. From the immoral features attributed to these servants by their masters comes the present scornful meaning of the word blackguard "scoundrel".

A similar history is traced for the words: boor, churl, clown, villain.

Boor ( originally 'peasant') came to mean 'a rude awkward, ill-mannered person'

Churl (synonym to boor) means an ill - mannered fellow.

In present day English a social component is superseded by the evaluative meaning.

A similar case is present in the history of the word clown: the original meaning was also 'peasant' or 'farmer'. Now it is used in two variants 'a clumsy boorish man' and also 'one who entertains'.

The French borrowing 'villain' has sustained an even stronger pejoration: from 'farm servant' to present meaning 'scoudrel'.

The semantic changes preqceed in accordance with logical and psychological laws of thought, othewise changed words would never be understood and couldn't serve the purpose of communication.