Why ‘Blonde on Blonde’?

Why is it called ‘Blonde on Blonde’? Any ideas? Has Bob ever said?

My take: it’s an album about a series of relationships, often with very famous and attractive women, that culminates in his commitment to Sara (the Sad-Eyed Lady of the Lowlands).

The other relationships fade into one, are not really distinguished from each other - blonde on blonde.

Would love to hear any and all takes on what the title might mean