The Collaborative International Dictionary of English v.0.48:

Soncy \Son"cy\, Sonsy \Son"sy\, a. [Scot. sonce, sons,
   prosperity, happiness, fr. Gael. & Ir. sonas.]
   Lucky; fortunate; thriving; plump. [Prov. Eng. & Scot.]
   [1913 Webster] Sond