archaicisms - What happened to the “‑est” and “‑eth” verb suffixes in English?

What happened to them, and how were they once used? Straining my mind to sound archaic, I came up with the following:

Dost thou thinkest thou can escape thy sins?

and

Bringeth me mine armor and favorite sword.

I’d like to use these suffixes intelligently, so my questions are:
how are ‑est and ‑eth properly appellated in conjugations, and
when and why did they disappear?

Answer

Verb paradigm in King James English for think

   Singular             Plural
   --------------------------
1  (I)    think         (we)   think
2  (thou) thinkest      (you)  think
3  (he)   thinketh      (they) think

Imperative: think

Infinitive: (to) think

These unfamiliar suffixes are applied in the same context that the -s suffix is applied in Modern English; for example:

• He thinks.



• Thou thinkest.

  
  
  
  

  ---




• He shall go. (no -s suffix on go)



• Thou shalt go. (irregular verb form for shall; but again, no suffix on go)

During the Early Modern English period, the 2nd person singular suffix disappeared and the -th suffix in the third person was replaced by another suffix, -s, which spread from dialects in the northern parts of the country. Other conjugations, such as -e in the first person singular from Middle English, had already been lost.

This sort of change is known as paradigm leveling. There is no particular reason per se that this kind of change happens, but it is not uncommon in the languages of the world.