Least and Undermost

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.

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

Undermost adjective - Of, relating to, or located at the bottom.

Least and undermost are semantically related. Sometimes you can use "Least" instead an adjective "Undermost".