waif
A late Middle English term (Oxford Dictionaries) referring to a stray person or animal, especially a homeless child, found without an owner and quite by chance. Waif can also refer to an unclaimed piece of property found (as if washed up by the sea) or stolen goods abandoned by an absconding thief. I am currently reading The Snow Child by Eowyn Ivey, a beautiful novel about a such mysterious waif who enters the lives of a husband and wife on the Alaskan frontier ca. 1920.