Where does the expression “hand-in-glove” come from and What does hand in glove mean?

Originally, about three hundred years ago, those using the metaphor hand-in-glove worded it hand and glove, that is, being on terms of intimate relationship comparable to that of one’s hand and the glove for it.

But whether through elision, hand ‘n’ glove, or through deliberate intent to indicate even closer intimacy, a snuggling intimacy as it were, seventeenth-century hand and glove became nineteenth-century hand-in-glove.