The trade was universal enough to name people across unrelated languages. Smith, Schmidt, Kowalski, Kovács, Ferrari, Herrera, Haddad — one job, nine tongues that never met.
BlackSchwarz · Чорний · Fekete · Neri · Negro · Noir
How this is counted. The rule is a count: the same root has to be recorded as a surname in five or more languages. Four is not enough, and the fifth cannot be a guess — it has to be an attested surname of that language.
The frequency here — 11% — is measured against
159 surnames, which is our corpus and not the English language.
Run the same rule over a different corpus and the number will differ; what will not
differ is which surnames carry the marker, because that is decided by the string,
not by the sample.