It is the goal of logic to prove hypotheses like “All swans are white” or to induce them from observational data. Popper argued that this would require the inference of a general rule from a number of individual cases, which is inadmissible in deductive logic. However, if one finds one single swan that is not white, deductive logic admits the conclusion that the statement that all swans are white is false. Falsification thus strives for questioning, for falsification, of hypotheses instead of proving them.
For a statement to be questioned using observation, it needs to be at least theoretically possible that it can come in conflict with observation. A key observation of falsification is thus that a criterion of demarcation is needed to distinguish those statements that can come in conflict with observation and those that cannot. Popper chose falsification as the name of this criterion.