lowyoudaoicibaDictYouDict[low 词源字典]
low: English has two words low, of which surprisingly the ‘noise made by cattle’ [OE] is the older. It goes back ultimately to the onomatopoeic Indo-European base *klā-. This also produced Latin clārus (which originally meant ‘loud’, and gave English clear and declare), clāmāre ‘cry out’ (source of English acclaim, claim, exclaim, etc), and calāre ‘proclaim, summon’ (source of English council).

It produced a prehistoric Germanic *khlō-, whose only survivor other than English low is Dutch loeien. Low ‘not high’ [12] was borrowed from Old Norse lágr (source also of Swedish låg ‘low’). This goes back to a prehistoric Germanic *lǣgjaz, which was derived from the same base as produced the English verb lie ‘recline’.

=> acclaim, claim, clear, council, exclaim; lie[low etymology, low origin, 英语词源]
low (adj.)youdaoicibaDictYouDict
"not high," late 13c., from lah (late 12c.), "not rising much, being near the base or ground" (of objects or persons); "lying on the ground or in a deep place" (late 13c.), from Old Norse lagr "low," or a similar Scandinavian source (compare Swedish låg, Danish lav), from Proto-Germanic *lega- "lying flat, low" (cognates: Old Frisian lech, Middle Dutch lage, Dutch laag "low," dialectal German läge "flat"), from PIE *legh- "to lie" (see lie (v.2)).

Meaning "humble in rank" is from c. 1200; "undignified" is from 1550s; sense of "dejected, dispirited" is attested from 1737; meaning "coarse, vulgar" is from 1759. In reference to sounds, "not loud," also "having a deep pitch," it is attested from c. 1300. Of prices, from c. 1400. In geographical usage, low refers to the part of a country near the sea-shore (c. 1300, as in Low Countries "Holland, Belgium, Luxemburg," 1540s). As an adverb c. 1200, from the adjective.
low (v.)youdaoicibaDictYouDict
Old English hlowan "make a noise like a cow," from Proto-Germanic *khlo- (cognates: Middle Dutch loeyen, Dutch loeien, Old Low Franconian luon, Old High German hluojen), from imitative PIE root *kele- (2) "to shout" (see claim (v.)).
low (n.1)youdaoicibaDictYouDict
sound made by cows, 1540s, from low (v.).
low (adv.)youdaoicibaDictYouDict
early 13c., from low (adj.). Of voices or sounds, from c. 1300.
low (n.2)youdaoicibaDictYouDict
"hill," obsolete except in place names, Old English hlaw "hill, mound," especially "barrow," related to hleonian "to lean" (see lean (v.)). Compare Latin clivus "hill" from the same PIE root.