20 or more years missing
Names absent from every published list for at least 20 consecutive years inside their recorded period.
Measured only between two years that do have a ranking, so it is an absence inside the record rather than the years before or after it. An absence means the name was below every published list's cut-off in those years — not that it was unused, and not that anything caused it to return.
186 names, ordered by longest absence first.