Sag
late Middle English (as a verb): apparently related to Middle Low German sacken, Dutch zakken ‘subside’.
wiktionary
From late Middle English saggen, probably of Scandinavian/Old Norse origin (compare Norwegian Nynorsk sagga(“move slowly”)); probably akin to Danish and Norwegian sakke, Swedish sacka, Icelandic sakka, Old Norse sokkva. Compare also Dutch zakken and German sacken (from Low German).
sag ( uncountable)
etymonline
sag (v.)
late 14c., possibly from a Scandinavian source related to Old Norse sokkva "to sink," or from Middle Low German sacken "to settle, sink" (as dregs in wine), from denasalized derivative of Proto-Germanic base *senkwanan "to sink" (see sink (v.)). A general North Sea Germanic word (compare Dutch zakken, Swedish sacka, Danish sakke). Of body parts from 1560s; of clothes from 1590s. Related: Sagged; sagging.
sag (n.)
1580s, in nautical use, from sag (v.). From 1727 of landforms; 1861 of wires, cables, etc.
