Sadly, most Americans don't read Asterix, which might actually help with understanding the cis and trans prefixes. We have a phonetics rule in English, that's actually observed more often than not, that when C is followed by an I or an E, then the C is pronounced as an S. Thus, cis is pronounced sis. Same rule, btw, usually applies to G, which when followed by I or E, becomes zh or dzh. Thus, our pronunciation of German and gender.