the.com/blood bank

means A facility that collects, tests, stores, and distributes donated blood for medical use.

from A straightforward 20th-century compound: 'blood' plus 'bank' used in its sense of a reserve supply held for future need, the same metaphor behind 'memory bank' or 'seed bank.' The phrase is generally credited to the 1930s-40s, as hospitals began systematically storing donated blood rather than relying only on direct donor-to-patient transfusion — the word simply borrowed banking's logic of deposits, withdrawals, and reserves held against future emergencies.