... and was already a common insult, which is what made the character and his name part of the gag. The name told you what you needed to know about the character.
Toast soaked in milk is bland, and easy on the stomach, suitable for babies of various species that might need tending to (as on a farm), and what moms used for weaning human infants in the days before Pablum and Gerber.
So, as an insult, it means one is being called "baby food".
Milktoast isn't wrong. Milquetoast comes from a comic character whose name was a pun for the bland breakfast.
... and was already a common insult, which is what made the character and his name part of the gag. The name told you what you needed to know about the character.
Toast soaked in milk is bland, and easy on the stomach, suitable for babies of various species that might need tending to (as on a farm), and what moms used for weaning human infants in the days before Pablum and Gerber.
So, as an insult, it means one is being called "baby food".