least vs optimal

least

det
  • The most little; the smallest amount or quantity of something. 

noun
  • Something of the smallest possible extent; an indivisible unit. 

adv
  • Used for forming superlatives of adjectives, especially those that do not form the superlative by adding -est. 

  • In the smallest or lowest degree; in a degree below all others. 

prep
  • At least. 

  • What a stupid white privileged POS I am! Least I call myself out. 

  • 2019 December, Justin Blackburn, The Bisexual Christian Suburban Failure Enlightening Bipolar Blues, page 79 

optimal

adj
  • Describing a search algorithm that always returns the best result. 

  • The best, most favourable or desirable, especially under some restriction. 

noun
  • The best of its kind 

How often have the words least and optimal occurred in a corpus of books? (source: Google Ngram Viewer )