1 (Scottish literary) having an attractive and healthy appearance; strong and healthy; comely.
2 agreeable; good-natured
Judging from her round, sonsy, rosy face, you never could have imagined her to have been mad. (Susanna Moodie, Life in the Clearings versus The Bush)
She listened to the talk of the men with a faint smile about her weary lips, her eyes upon the sonsy range. (George Douglas Brown, The House With The Green Shutters)
Mid 16th century (also in the sense 'lucky'): from Irish and Scottish Gaelic sonas 'good fortune' (from sona 'fortunate') (Oxford English Dictionary)