worst (adj.) Look up worst at Dictionary.com
Old English wyrresta, from Proto-Germanic *wers-ista- (cf. Old Saxon wirsista, Old Norse verstr, Old Frisian wersta, Old High German wirsisto), superlative of PIE *wers- "to confuse, mix up" (see worse). Phrase in the worst way (1839) is from American English sense of "most severely."
worst (v.) Look up worst at Dictionary.com
"damage, inflict loss upon," c.1600, from worst (adj.). Related: Worsted; worsting.