"boundary," late 13c. (in reference to the borderlands beside Wales, rendering Old English Mercia), from Old French marche "boundary, frontier," from Frankish *marka or some other Germanic source (compare Old High German marchon "to mark out, delimit," German Mark "boundary;" see mark (n.1)). Now obsolete.
There was a verb in Middle English (c. 1300), "to have a common boundary," from Old French marchier "border upon, lie alongside." This is the old Germanic word for "border, boundary," but as it came to mean "borderland" in many languages new words were borrowed in the original sense (compare border (n.), bound (n.)"border, boundary"). Modern German Grenze is from Middle High German grenize (13c., replacing Old High German marcha), a loan-word from Slavic (compare Polish and Russian granica). Dutch grens, Danish groense, Swedish gräns are from German.