Court cases and pension applications often contain affidavits and statements from witnesses. Sometimes these statements will indicate how long the person providing testimony had known the applicant or one of the parties involved in the case. Think about how long that was. Was it when the parties involved lived somewhere else?
Maybe if you can't trace the person of interest back in time and place, you can trace the witness to a previous residence and then may find the person of interest hanging out in the same location.