What is the orgin of the slang term main sqeeze?

Answer 1

The image is of someone you hug tightly, or squeeze. He or she is your "main" hugger (or "hug-ee") and so they are your "significant other."

Answer 2

The slang term "main squeeze" originated in the 19th century and is believed to have derived from the idea of someone being the "main" or primary person in a romantic relationship, likened to squeezing a lemon to get the juice out, emphasizing the close bond between two people.