In a manner characterized by bowing; with the gesture or motion of bending at the waist as a sign of respect or greeting.
From 'bowing' (present participle of 'bow') plus the adverb suffix '-ly'. Constructed in the regular manner of forming adverbs in English.
Adverbs like 'bowingly' are becoming rare in modern English, but they show how creatively older English speakers could describe physical actions—you could literally see the bowing happening in the word!
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