In all seriousness, it is most likely vodka. The whole point of vodka is to make it as tasteless and smooth as possible. (I'm talking true vodka here, not that flavored shit Absolute or Three Olives puts out) whereas all other spirits go out of their way to make it taste like "something".
I remember someone once telling me that is how vodka "martinis" and "vodka tonics" all started becoming popular.
Back it the 60's and 70's, it wasn't unusual for business men to have a couple of drinks on their lunch break, hence the "Three Martini Lunch".
But, gin is always infused with herbals, the most predominant of which being juniper, would make you come back to work smelling like an old xmas tree.
So, they started making these drinks with...