First photo: Harley Earl's 1938 Buick Y-Job Concept (front view)

Second photo: Harley Earl's 1938 Buick Y-Job Concept

Third photo: Harley Earl in the Y-Job

Note from Wikipedia article: All experimental cars were called "X", so Earl simply went to the next letter in the alphabet. The "Y" designation was selected by Earl because it was used extensively in the aviation industry denoting the most advanced prototypes.