A language or collection of dialects that descended from Old Saxon and is the ancestor of modern Low Saxon, spoken from about 1100 to 1600.
1989, P. Sture Ureland, Some contact structures in Scandinavian, Dutch, and Raeto-Romansh: inner-linguistic and/or contact causes of language change, in: Leiv Egil Breivik, Ernst Håkon Jahr (eds.), Language Change: Contributions to the Study of its Causes (= Trends in Linguistics: Studies and Monographs 43), p. 267:
Furthermore, there was another cultural movement which also changed the map: that of Middle Low Saxon (the language of the Hanseatic League) which brought zik-forms into north-eastern Dutch dialects in Twente and Groningen during the period of the Hanseatic League, the 13th and 15th centuries, after the Middle High German sich had been adapted to sik (cf. [...]).
2018, Elżbieta Adamczyk, Reshaping of the Nominal Inflection in Early Northern West Germanic, page 252:
Their linguistic profile [= the linguistic profile of the later sources of Old Frisian] corresponds rather to that found in contemporaneous languages from the surrounding areas, namely, Middle Dutch, Middle Low Saxon, or Middle English, which attest a more advanced stage of phonological, morphological and, more generally, typological development.
2001, edited by Horst Haider Munske in collaboration with Nils Århammar, Volker F. Faltings, Jarich F. Hoekstra, Oebele Vries, Alastair G.H. Walker, Ommo Wilts, Handbuch des Friesischen / Handbook of Frisian Studies, p. 587:
Middle Low German - also referred to in Frisian scholarship as (Middle) Low Saxon - had all but replaced Frisian in writing east of the Lauwers by the mid-15th century.
2020, Jan Rüdiger, translated by Tim Barnwell, All the King’s Women: Polygyny and Politics in Europe, 900–1250, p. 158:
Ebel also calls attention to the related Old High German ella, Middle Low Saxon elle "Nebenbuhlerin, Konkubine."
