Definition from Wiktionary, the free dictionary
There are two etymological paths whose accuracy and possible interrelation are not conclusively established.
- Schlucht is most readily explained as a Middle Low German form of the archaic High German equivalent Schluft, with the Low German development of -ft- → -cht- (cf. Nichte). Schluft pertains to the verb schliefen (“to slip, to move through”). This etymology is favoured by most authorities, although they seem to be unable of attesting the Middle Low German word.
- There is an Upper German attestation of Middle High German wazzersluht or possibly -slůht (“water-filled ditch”), which is in line with similar words in modern Upper German dialects. Some of these words also mean “cut-off branch” and may pertain to schlagen (“to hew”). The sense of “ditch” might be derived from “branch”.
- Schlucht in Duden online