E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Learn by Heart (To).
The heart is the seat of understanding; thus the Scripture speaks of men wise in heart; and slow of heart means dull of understanding. To learn by heart is to learn and understand; to learn by rote is to learn so as to be able to repeat; to learn by memory is to commit to memory without reference to understanding what is so learnt. However, we employ the phrase commonly as a synonym for committing to memory.