In epistemology the prefix meta- is used to mean about (its own category). For example, metadata is data about data (who has produced it, when, what format the data is in and so on). Similarly, meta-memory in psychology means an individual's intuition about whether or not they would remember something if they concentrated on recalling it. Any subject can be said to have a meta-theory, which is the theoretical consideration of its foundations and methods.
The prefix is derived from the Ancient Greek meta, which is a preposition and prefix having several meanings. One of those, meta as preposition taking the genitive case, translates as the English with; but there are others, and the verb prefix meta- in Greek, seen in metamorphosis, connotes change.
The current English usage is accidental, deriving from the classification of Aristotle's works to include the category of metaphysics, which could more or less be described as the study of the physics of physics itself. This was initially merely the extras left over from the physics category.
See also