How Keigo was born.

Keigo seems to have derived from two sources of ideas in ancient Japan.

One is the thought of “kotodama（言霊）”, which means that words/phrases,
when uttered, can embody the spirit of the speaker.This idea forced ordinary people to express admiration for their superiors,
especially when the importance of good human relationships had become the social norm.
The other is related to a set of words/phrases that were forbidden
because they can have a direct reference to the superiors of ordinary people,
including women and children.
This was because making a direct reference
about a senior person was perceived as socially unacceptable.
Therefore women and children once could not address their masters i.e. husbands and fathers
in a direct manner.
Thus, these lower-ranking people had to invent a way
in which they could address their superiors indirectly.

These two ideas of admiration and making an indirect reference
to superiors have contributed the development of Keigo.
A lot of Keigo words have derived from words that had no bearing on respect.
When ancient people received a gift from a high-ranking official, they quite often lowered their heads with both their hands up high.
One of the best words to describe this behaviour was ‘itadaku　（いただく）’, which literally meant ‘to place something above one’s head’. In this way the verb ‘itadaku’ acquired the meaning of receiving a gift from somebody high up.This represents the process through which words have acquired honorific meanings.
Different processes gave birth to the various aspects of Keigo.