Correct spelling for the English word "werts" is [wˈɜːts], [wˈɜːts], [w_ˈɜː_t_s] (IPA phonetic alphabet).
The word "werts" is a contraction of "wert thou", which is an old second-person singular form of the verb "to be" in Early Modern English. "Wert" is derived from the Old English word "wæron", which means "were". The contraction "werts" has its roots in Middle English and was commonly used in the 16th and 17th centuries.