深谙 is bookish / literary. The everyday equivalents are 非常了解, 精通 (master / be proficient in), or 熟悉 (familiar with). 深谙 implies not just knowledge but practiced wisdom, used for someone who has internalized a domain.
memory
深 (deep) + 谙 (be familiar with, 言 speech radical + 音 sound, picturing someone who has heard much). Together: "deeply heard / acquainted" → has lived with it long enough to know it cold.
