An Inquisition

Here is a little table of words that clearly have an etymological relationship. The puzzle is to explain the function of the the quis root and how it combines with the prefixes to form the words, whose meanings, in turn, must have evolved somewhat over time.

acquisitionacquireacquest acquisitive
disquisition   disquisitive
inquisitioninquireinquest inquisitive
question quest  
sequestration sequester,sequestrate  

And why don't equestrian, esquire, quire and squire belong?

Last modified on 11 May 2020.