In one of Nestor's chronicles from the 12th century he mentions a lake called "the Great Nevo", a clear link to the Neva River and, possibly furthermore, to Finnish nevo "sea" or neva "bog, quagmire".
Ancient Norse sagas and Hanseatic treaties both mention a city made of lakes named Old Norse Aldeigja or Aldoga. Since the beginning of the 14th century this hydronym was commonly known as Ladoga. According to T. N. Jackson, it can be taken "almost for granted, that the name of Ladoga first referred to the river, then the city, and only then the lake." Therefore, he considers the primary hydronym Ladoga to originate in the eponymous inflow to the lower reaches of the Volkhov River whose Finnic name was Alodejoki (corresponding to modern Finnish: Alojen joki) "river of the lowlands".
The Germanic toponym (Aldeigja → Aldoga) was soon borrowed by the Slavic population and transformed by means of the Old Russian metathesis ald- → lad- to Old East Slavic: Ладога. The Old Norse intermediary word between Finnish and Old Russian word is fully supported by archeology, since the Scandinavians first appeared in Ladoga in the early 750s, that is, a couple of decades before the Slavs.
Other theories about the origin of the name derive it from Karelian: aalto "wave" and Karelian: aaltokas "wavy"; or from the Russian dialectal word алодь, meaning "open lake, extensive water field". Eugene Helimski by contrast, offers an etymology rooted in German. In his opinion, the primary name of the lake was Old Norse: *Aldauga "old source", associated to the open sea, in contrast to the name of the Neva River (flowing from Lake Ladoga) which would derive from the German expression for "the new". Through the intermediate form *Aldaugja, Old Norse: Aldeigja cam about, referring to "Ladoga (city)".