Correct me, if I am wrong, but it is because BMW is a abbreviation for the automobile corporations’ founder(s) & BMX is a abbreviation for the dirt bicycling racing. Without any corrections given… So what would you think replacing- BMW’s W with a Y mean? What would Y & BMX’s X with a Z mean? What would Z

be abbreviations for & how would think they work with the other words, within each abbreviation (hope that understood)?

I’m pretty sure BMW stands for something like Bayer Motor Works but in German.