All very true. But later in the novel, it’s explained that the literal meaning is “to drink.”
However, in the last 50 years or so--every time I've come across it and every time I've used it--it has meant TO KNOW, TO UNDERSTAND comprehensively, immersively. Your mention of it meaning to drink is the first I can recall hearing of that meaning.
I guesstimate I've come across it or used it about a couple dozen times or so in the last 50 years.