Synonyms of foundling
strayStray is also a noun.
• The dog was a stray which had been adopted.
waifIf you refer to a child or young woman as a waif, you mean that they are very thin and look as if they have nowhere to live.
• an emaciated waif living rough on the streets
Thesaurus for foundling from the Collins English Thesaurus
an abandoned infant whose parents are not known