Here's a Sanka commercial from 1959, the year this ad ran in Life Magazine. Is "flavorsome" a word? I'm doutious it is. And when did we add the extra "E" to the end of "caffein"? Collins Dictionary says it's from the german word "kaffein", which is from their other word "kaffee". Dictionary.com says "also 'caffein'". BORR-IIING! Which means it's probably the whole story.
And here's one from The Seventies with a chorus of excited people singing how great it is to be the third largest coffee in America. No kidding. You'd think it would sound better to say you're "the leading decaffeinated coffee in America" than "the third largest coffee in America", right? I guess The Seventies weren't about achievement, were they?