For any British form you have to fill in, you have to mention your surname. Never, or rarely, someone asks you for your surnom in French. If ever it happens, you have to tell your nickname. Whereas surname in French would be requested as is nom de famille (family name) or, in a formal language it would be patronyme (patronymic).
Surnom and surname are not only false cognates, but their pronunciations are also different, especially because surnom contains one of those specific to French, nasal vowels : ‘on‘ which can be written ‘on‘ or ‘om‘. Listen!
Sais-tu que les surnoms de Shakespeare (1564-1616, Stratford-upon-Avon) sont le ‘barde d’Avon‘ et le ‘barde immortel’? (Do you know that Shakespeare’s nicknames are the ‘Bard of Avon’ and the ‘Immortal Bard ?).
Barde in French and bard in English are pronounced the same way and have both, the same meaning and origin: poet in the medieval Gaelic language. The word isn’t much used anymore.
Immortel and immortal are the same word. At least this one is easy!
Surnom = nickname
Nom de famille = surname
What about a little quiz concerning celebrities’ nicknames? Click and give it a go!