Least and Primaeval

Least adjective - The superlative of `little' that can be used with mass nouns and is usually preceded by `the'; a quantifier meaning smallest in amount or extent or degree.

Primaeval and least are semantically related. In some cases you can use "Primaeval" instead an adjective "Least".

Primaeval adjective - Having existed from the beginning; in an earliest or original stage or state.

Least and primaeval are semantically related. Sometimes you can use "Least" instead an adjective "Primaeval".