Is it permissible to name an abandoned child after their guardian, knowing the well-known reasons for doing so?

It is permissible to name a foundling with any legitimate name, but it is not permissible for their guardian to attribute them to themselves. Rather, they should be attributed to 'Abdullah (servant of Allah) or 'Abdur-Rahman (servant of the Most Merciful), and similar names. Islam has forbidden adoption, as Allah Almighty says: "Call them by their fathers' names; that is more just in the sight of Allah. But if you do not know their fathers' names, then they are your brethren in faith and your Mawali (protectors/associates)."