To infect with or cause canker (a disease or corruption); to make something diseased or morally corrupt.
From en- + canker (from Latin cancer, meaning crab or malignancy). The verb form emerged to describe the spreading of disease or corruption.
Shakespeare and Milton used 'encanker' for moral corruption spreading like disease—'encanker'd roses' meant rotting flowers. It's poetic medicine, where words about physical disease describe spiritual sickness!
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