All of these words have the same partial etymology of "cide," which means "cut" or "kill." The word "decide" actually means to make a choice by cutting or killing the other choices. In other words, at it's core, deciding means choosing by process of elimination.
Of course, the word "decide" isn't used that specifically. No dictionary will specify that a decision is only a process of elimination. Words don't always have the same exact meanings as what their roots might suggest, but it's interesting to see the connection between words with similar etymologies.
At first it may seem as though some words have nothing to do with others of the same root, but often there's a connection somewhere. Knowing the meanings of word roots can be pretty useful when you come across a word you don't know the meaning of. It allows you to make an educated guess and possibly get a general meaning based on the context.
