Borrowed from Russian and Ukrainian Со́ня (Sónja), an informal pet form of Со́фья (Sófʹja), Софі́я (Sofíja) or Софи́я (Sofíja, “Sofia, Sophia”), from the Ancient Greek σοφία (sophía, “wisdom”). It was introduced into English through 19th century Russian literature and taken into general use in early twentieth century.