"Argument of \OT1\" has an extra }" when I have an umlaut in the name

Question

I'm trying to compile the following MWE:

\documentclass{article}

\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@article{ab_cd_2015,
  author = {{N{\"o}me}, Name},
  year         = {2014},
  title        = "Why Is Apple Launching a New Version of the {{iPod}}?"
}

\end{filecontents}

\begin{document}

Random citation \cite{ab_cd_2015} embeddeed in text.

 % acm, plain works
 % alpha, alphadin, alphaurl, geralpha work not
\bibliographystyle{alpha}
\bibliography{\jobname}

\end{document}

When I compile this, I get:

(./mwe.aux) (./mwe.bbl
! Argument of \OT1\" has an extra }.
<inserted text> 
                \par 
l.1 \begin{thebibliography}{{N{\"}}14}

When I change author to either {N{\"o}me, Name}, {{N{o}me}, Name} or {N\"ome, Name} it compiles fine. What is it about {{N{\"o}me}, Name} that triggers the error? I generate the BibTeX from Zotero, and I'm trying to come up with rules that generate working BibTeX, this one has me stumped.

Answer 1

The field

author = {{N{\"o}me}, Name},

is malformed, according to the (complex) rules of BibTeX, because it produces the faulty entry

\bibitem[{N{\"}}14]{ab_cd_2015}

in the .bbl file.

Essentially, the inner braces are ignored, so you end up as if the name was

N\"ome

which would produce almost the same, that is,

\bibitem[N\"14]{ab_cd_2015}

The only difference are the missing braces.

With

author = {N{\"o}me, Name},

you get the correct

\bibitem[N{\"o}m14]{ab_cd_2015}

Note that the number of letters is as expected, that is, three. Also in the previous cases there are three tokens, but not the ones LaTeX expects.