lectio difficilior potior → the more difficult reading is the stronger
Lectio difficilior potior (Latin for "the more difficult reading is the stronger") is a main principle of textual criticism. Where different manuscripts conflict on a particular reading, the principle suggests that the more unusual one is more likely the original. The presupposition is that scribes would more often replace odd words and hard sayings with more familiar and less controversial ones, than vice versa. It will readily be seen that lectio difficilior potior is an internal criterion, which is independent of criteria for evaluating the manuscript in which it is found, and that it is as applicable to manuscripts of a roman courtois or a classical poet as it is to a biblical text.
Lectio difficilior potior - Wikipedia