From Middle English selli, sellich, from Old English sellīc, seldlīc (“rare, strange, wondrous, extraordinary, wonderful; having unusually good qualities, excellent, admirable; select, better, superior, choice”), equivalent to seld + -ly. Cognate with Scots selly, silly (“approved, good, worthy”), Old Saxon seldlīk (“rare, wonderful”), Gothic 𐍃𐌹𐌻𐌳𐌰𐌻𐌴𐌹𐌺𐍃 (sildaleiks, “wonderful”).
- (Britain dialectal, Northern England, Scotland) Wonderfully, wondrous.
- His brother was.. selly sick and sore unsound.
selly (plural sellies)