The saying originated from the 1937 song Let's Call the Whole Thing Off by George and Ira Gershwin. In the song, the two pronounciations of "tomato" are compared: "tuh-may-toe" and "tuh-mah-toe". When people say "tomato tomahto" they say both pronounciations, as they were compared in the song.
by CelticEagle February 21, 2019