"Wert sure" is not a commonly used phrase in English. However, the spelling of this word can be explained with IPA phonetic transcription. "Wert" is pronounced as /wərt/ and is the archaic form of "were", which means "were you". "Sure" is pronounced as /ʃʊər/ and means "certain". When combined, "wert sure" implies asking someone if they are certain about something in the past. Although not frequently used now, it was common in older forms of English.