The word "wert negligent" may look unfamiliar and confusing to some, but it is simply an archaic form of the phrase "were negligent." In IPA phonetic transcription, it would be spelled /wɜːt nɛɡlədʒənt/ with the stressed syllable on "negligent." This spelling reflects the pronunciation of English during the Middle English era, which used "wert" instead of "were" and did not have standardized spelling. While rare today, such archaic spellings can be found in older works of literature or historical documents.
The phrase wert negligent does not have a specific etymology because wert is not a standalone word, and negligent is derived from the Latin word negligentem. However, if we break it down, wert is the archaic second-person singular past tense of the verb to be in Middle English, which evolved into were in modern English. So, the phrase can be understood as were negligent. The word negligent ultimately derives from the Latin word negligere, meaning to neglect or to disregard.