Correct spelling for the English word "foolest" is [fˈuːləst], [fˈuːləst], [f_ˈuː_l_ə_s_t] (IPA phonetic alphabet).
The word foolest is derived from the Old English term fule or ful, which means foolish or silly. Over time, this word evolved and became fool, which refers to someone who lacks intelligence or acts in a foolish manner. Foolest is the superlative form of fool, meaning most foolish.