Ingvaeonic, also known as North Sea Germanic, is a postulated grouping of the West Germanic languages that comprises Old Frisian, Old English and Old Saxon. Ingvaeonic is named after the Ingaevones, a West Germanic cultural group or proto-tribe along the North Sea coast. It is not thought of as a monolithic proto-language, but rather as a group of closely related dialects that underwent several areal changes in relative unison.. The grouping was proposed by German linguist Friedrich Maurer as an alternative to the strict tree diagrams which had become popular following the work of 19th century linguist August Schleicher and which assumed the existence of a special Anglo-Frisian group.

Characteristics

Linguistic evidence for Ingvaeonic are common innovations observed in Old Frisian, Old English and Old Saxon such as the Ingvaeonic nasal spirant law, the loss of the Germanic reflexive pronoun, the monophthongization of Germanic *ai to ē/ā, and deflexion such as the reduction of the three Germanic verbal plural forms into one form.