An Etymological Dictionary of the German Language/Annotated/Mark
Mark (1.), feminine, ‘marches, frontier,’ from Middle High German marc, ‘mark, token,’ Old High German marcha, feminine, ‘frontier, marches’; compare Old Saxon marca, ‘territory,’ Anglo-Saxon mearc, feminine, ‘frontier, territory’ (English march is not based on the Anglo-Saxon form, the c of which would not have changed to ch, but on Old French marche, ‘frontier,’ which is of Teutonic origin). To Gothic marka, feminine, ‘frontier,’ corresponds Old Icelandic mǫrk, ‘wood,’ with a remarkable change of meaning; woods in Teutonic times were often the natural boundaries between nations. The originally meaning of the cognates of ‘frontier’ is supported by their primitive kinship with Latin margo, ‘border,’ as well as by Old Irish brú (from the primary form *mrog), ‘border,’ Irish bruig, Welsh and Cornish bro, ‘district, country, region,’ Modern Persian marz, ‘frontier, marches.’ From Teutonic are derived Italian marca, French marche, ‘frontier.’ See Mark (2) and Marke.
Mark (2.), feminine, ‘mark’ (coin), from Middle High German marc, marke, feminine, ‘mark, half a pound of silver or gold’; Old High German *marka (whence Middle Latin marca, which first appears in documents in the latter half of the 9th century), Anglo-Saxon and Middle English marc, Old Icelandic mǫrk, feminine, ‘mark, half a pound of silver.’ Its origin is obscure; the assumption that Marke, ‘designation, sign’ (with reference to the stamp), is a cognate, is not proved, since Mark originally denoted a definite weight, and not a particular coin.
Mark (3.), neuter, from the equivalent Middle High German marc (genitive marges), neuter, ‘marrow, pith’; the Middle High German g has been preserved in mergeln; Old High German marg, marag, neuter, Old Saxon marg, neuter, Dutch merg, neuter, Anglo-Saxon mearg, neuter, English marrow, Old Icelandic mergr, masculine, ‘marrow’; in this word r is due to Gothic z, according to the law of rhotacism; Gothic *mazga- is wanting. The latter points to pre-Teutonic *mazgho-, to which Old Slovenian mozgŭ, masculine, Zend mazga, Sanscrit majjan, ‘marrow,’ all with a normal loss of the aspirate, correspond. The root is Sanscrit majj, ‘to immerse,’ to which Latin mergere is allied.