soothyoudaoicibaDictYouDict[sooth 词源字典]
sooth: [OE] Sooth ‘truth’ (which now survives in current usage only in the compound soothsayer [14]) goes back ultimately to Indo-European *sntyós (possible ancestor also of English sin). This was a derivative of the base *es- ‘be’, and hence etymologically means ‘that which is’. It passed into prehistoric Germanic as the adjective *santhaz.

As in English, in most other Germanic languages the word has now died out, but it survives in Swedish (sann) and Danish (sand) as an adjective meaning ‘true’. From the Old English form sōth a verb was formed, sōthian ‘prove to be true’, which has evolved into modern English soothe. Its present-day meaning did not emerge, via intermediate ‘confirm’ and ‘please or flatter by confirming or agreeing’, until the 17th century.
=> soothe[sooth etymology, sooth origin, 英语词源]
sooth (n.)youdaoicibaDictYouDict
Old English soð "truth, justice, righteousness, rectitude; reality, certainty," noun use of soð (adj.) "true, genuine, real; just, righteous," originally *sonð-, from Proto-Germanic *santhaz (cognates: Old Norse sannr, Old Saxon soth, Old High German sand "true," Gothic sunja "truth").

The group is related to Old English synn "sin" and Latin sontis "guilty" (truth is related to guilt via "being the one;" see sin (v.)), from PIE *es-ont- "being, existence," thus "real, true," from present participle of root *es-, the s-form of the verb "to be" (see be), preserved in Latin sunt "they are" and German sind. Archaic in English, it is the root of modern words for "true" in Swedish (sann) and Danish (sand). In common use until mid-17c., then obsolete until revived as an archaism early 19c. by Scott, etc. Used for Latin pro- in translating compounds into Old English, such as soðtacen "prodigy," soðfylgan "prosequi."