Both in Spanish and Catalan, the word for "comrade" is "camarada", as you wisely guessed. This word has been historically used by Communists, Falangists (fascists) and Anarchists. However, the word "compañero" (lit. colleague) was more common among Spanish Anarchists. I'm sure other answers can give us wider and better documentation, but as an example, you can check this letter by CNT leader Buenaventura Durruti where he used the word "compañeros": https://es.m.wikisource.org/wiki/A_los_obreros_rusos_(B.Durruti) I'm sure it may be translatable to the specific case of Catalonia. The word in Catalan is "company", and it's widely used by Catalan anarchists today. Though I don't know examples of its use during the Civil War, I think it's likely. I'm sure other users can bring us more light on the issue.