In the Little House book series, Pa often refers to Laura as half-pint, or in an expanded version of the nickname as “my little half-pint of sweet cider half drunk up.”
But in today’s world, the measurement half pint is no longer commonly used, so many don’t understand the meaning behind the phrase today.
Pa was essentially referring to Laura’s small size as a child, and also in reference to Laura being smaller than her older sister Carrie.
In specific size terms, a half-pint is a size of a liquid serving, which is the equivalent of 1 cup. So this would be the size of a smaller glass, with a regular glass often being a pint in size.