A shy, childlike smile is an example of a winsome smile.
Origin of winsomeMiddle English winsum ; from Old English wynsum, pleasant, delightful ; from wynn, delight, joy (for Indo-European base see win) + -sum, -some
Origin of winsomeMiddle English winsum, from Old English wynsum : from wynn, joy; see wen-1 in Indo-European roots + -sum, characterized by; see –some1.
(comparative more winsome, superlative most winsome)
From Middle English, from Old English wynsum (“winsome, pleasant, joyful, merry"), from Proto-Germanic *wunisamaz (“joyful"), from *wunjÅ (“joy, delight, desire"), from Proto-Indo-European *wun-, *wenÇ- (“to wish, love"), equivalent to winne +"Ž -some. Cognate with Scots winsome, wunsome (“charming, comely, pleasing"), Middle High German wunnesam (“winsome, joyful, delightful"), Old English wynn (“joy, rapture, pleasure, delight"), German Wonne (“bliss, delight, joy"). More at winne, winly.