English has its roots in the languages of several more-or-less-pagan Germanic peoples who migrated into the British Isles about 550 A.D, just half-a-century or so after the fabled more-or-less-Christian King Arthur had reigned in those lands. The English of this period is the true "Old English", and is the language of Beowulf.
About 500 years later, after the Normans (from France) invaded England around 1066, the language morphed into Middle English. It was this variant of the language that reigned until about the 1450s.
For the next couple of hundred years, from the mid-15th century until about 1650, the Brits spoke Early Modern English. It was during this period that the King James Bible was produced. This version of English, also known as Renaissance or Elizabethan English, is also the language of William Shakespeare.
Today we speak Modern English, which is but an update of the King's English.
So strictly speaking, the language of the King James Bible is not Old English, but is rather Early Modern English.
Still, it seems quite old to many of us in the 21st century.
The main idea I wish to convey in this post, however, concerns a couple of points of grammar, specifically the forms of thee, thou, ye, thy, thine, and the -est and -eth verb endings.
The use of thee, thou, etc, is fairly simple. It has nothing to do with respect or reverence; it has to do with how many people are being addressed. If you were speaking to one person, you would use "thee", "thou", "thy", or "thine". If you were speaking to a group of people, you'd use "you" or "ye".
- thou - if the person is the subject ("you give it to me"), you'd use "thou" ("thou givest it to me")
- thee - if the person is not the subject ("I'll give it to you"), you'd use "thee" ("I'll give it to thee")
- ye - if the group is the subject ("y'all give it to me"), you'd use "ye" ("ye give it to me")
- you - if the group is not the subject ("I'll give it to y'all"), you'd use "you" ("I'll give it to you")
I think the take-home lesson from this is that when you see "thee", "thine", "thou", "or "thy", you can know that the case of the person being addressed is singular. When you see "you" or "ye" or "your" or "yours", the case is plural.
Concerning the verb endings -est and -eth, the basic rule is that both are singular forms, with the "-est" indicating second-person-plural, and with the "-eth" indicating third-person plural:
- I love thee.
- Thou lovest me.
- She loveth me.
- They love me.
(This is my understanding, and I don't claim it to be a perfect or accurate understanding. Most of my education on the topic is from http://www.kjv-only.com/theethou.html.)