Seldomly is from a nonstandard 'seldom' + '-ly'; 'seldom' is from Old English 'seldan' ('rarely'), from Proto-Germanic *selda- ('rare, strange'). The historical chain includes Old English seldan and Proto-Germanic *seldaz. Older glosses in the chain include "seldom", "-ly", "seldan", and "rarely", which help explain the semantic range of the modern word. Morphologically, seldomly is best read as compound and borrowing, yielding an English adverb shaped by both form history and later usage. In current English it functions as an adverb, with the sense "on rare occasions; not often (nonstandard variant of seldom)". related forms include seldom. The result is an English adverb whose etymology preserves the older forms while supporting the word's specialized modern meaning.