In a manner expressing dependence or the act of depending; while depending on something.
From depending (present participle of depend) plus -ly (adverbial suffix). This creates an adverb from the gerund form, a less common but grammatically valid English formation.
You rarely see 'dependingly' in modern writing because it sounds archaic, but it appears in older literature and poetry where writers needed to describe an emotional state of relying on someone—it captures a plaintive tone.
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