Sonsy is from scots and Irish dialect, from sonse ('abundance, good fortune, prosperity') + -y, from Scottish Gaelic sonas ('good fortune, happiness'). The historical chain includes Scottish Gaelic sonas. Older glosses in the chain include "abundance, good fortune, prosperity" and "good fortune, happiness", which help explain the semantic range of the modern word. Morphologically, sonsy is best read as compound and suffixal formation, yielding an English adjective shaped by both form history and later usage. In current English it functions as an adjective, with the sense "buxom, healthy-looking, and cheerful (Scots and Irish dialect)". The result is an English adjective whose etymology preserves the older forms while supporting the word's specialized modern meaning.