Meaning: everything; wholly; completely.
My mother had laughed at me. “Do you think they’ll take someone like you, right off the bat? Why you’ve got to know all these catechisms and credos and believe in them, lock, stock and barrel. A girl with your sense!”
Sylvia Plath, “The Bell Jar”, 1963
From the principal parts of a flintlock. First Known Use: 1842
Source: Merriam-Webster & Free-Dictionary