What is the Latin word for surname?

The usual Latin words for “surname” are cognōmentum, indō. The right choice depends on the sense; see the distinctions below.

English → Latin

“surname” in Latin

cognōmentumsurname; name indōto put, set or place into or upon; insert, instill, introduce; to introduce; to impart or give to, apply to, impose on,

Riddle & Arnold A Copious and Critical English–Latin Lexicon, 1864

surname

cognomen, cognomentum (very rare in Cic.: agnomen, late). To give a surname to anyone, cognomen imponere, indere, alicui: to assign a surname to anyone, cognomine aliquem appellare: Aristides bore the surname of Just, Aristides cognomine Justus appellatus est: to derive a surname from anything, cognomen trahere ex re.

Quick answer

What is the Latin word for surname?: The usual Latin words for “surname” are cognōmentum, indō. The right choice depends on the sense; see the distinctions below.

Entry from J. E. Riddle & T. K. Arnold, A Copious and Critical English–Latin Lexicon (rev. C. Anthon, New York: Harper, 1864), digitised by Fergus J. P. Walsh, CC BY-SA 4.0; Latin markup adapted by latindictionary.co.