David's patch is good, but it can be largely improved, for instance making the name language aware and adding easy support for changing the formatting of the header.
\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[english,czech]{babel}
\usepackage{pseudocode}
\usepackage{xpatch}
% fix the bad code in pseudocode.sty
\xpatchcmd\pseudocode{\bfseries Algorithm }{\algorithmheadformat\algorithmname\ }{}{}
\xpatchcmd\pseudocode{\bfseries Algorithm }{\algorithmheadformat\algorithmname\ }{}{}
\providecommand{\algorithmname}{Algorithm}
\providecommand{\algorithmheadformat}{\bfseries}
% end of fix
\addto\captionsczech{\renewcommand{\algorithmname}{Algoritmus}}
\addto\captionsenglish{\renewcommand{\algorithmname}{Algorithm}}
\renewcommand{\algorithmheadformat}{\scshape}
\begin{document}
\begin{pseudocode}{CelsiusToFahrenheit}{c}
f \GETS {9c/5} + 32\\
\RETURN{f}
\end{pseudocode}
\selectlanguage{english}
\begin{pseudocode}{CelsiusToFahrenheit}{c}
f \GETS {9c/5} + 32\\
\RETURN{f}
\end{pseudocode}
\end{document}
I added \renewcommand{\algorithmheadformat}{\scshape} just by way of example.

\ALG@namewhich won't help here, – David Carlisle Apr 24 '17 at 22:21