An obsolete or dialectal form representing 'did not' in very old English, no longer used in modern speech or writing.
From Middle English 'dide' (did) combined with 'ne' (not), which contracted over centuries into 'didn't'; this entry represents an intermediate or non-standard form rarely documented.
This shows how English contractions are constantly evolving—the 'n't' we use today came from the word 'not' literally squishing onto verbs, and 'didn' represents a snapshot of that messy middle ground between old and new English.
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