E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
means heart to heart. (Latin, ad corda.) If two persons like and dislike the same things, they are heart to heart with each other.
Similarly, con-cord means heart with heart; dis-cord, heart divided from heart; re-cord properly means to recollecti.e., re-cordre, to bring again to the mind or heart; then to set down in writing for the purpose of recollecting.