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.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894