In the original French Tournesol (Calculus) is accused of acting like a "zouave" (
à faire le zouave). Haddock quite often used
zouave as an insult in the original editions.
Zouave was the name of a regiment in the French army (see the relevant wikipedia page
here).
The zouave were known for their courage and bravery. Hence, from what I can gather, Calculus most likely took offence to this insult because he was "acting the zouave", i.e. he was a fraud, pretending to be courageous rather than really being it.
I hope that's right, I'm sure someone will correct me otherwise!