A coming toward or arrival at a place; the act of approaching or drawing near (obsolete or very rare term).
From 'advent' (arrival) plus the suffix '-ry' (forming nouns of action or practice). This is an archaic formation that never became standard in English.
This word is so rare that it barely appears in modern dictionaries, but it represents an Old English pattern of word-formation that helped create many common words—most speakers have never encountered 'adventry' in their lives.
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