booyoudaoicibaDictYouDict[boo 词源字典]
expression meant to startle, early 15c., boh, "A combination of consonant and vowel especially fitted to produce a loud and startling sound" [OED, which compares Latin boare, Greek boaein "to cry aloud, roar, shout."]; as an expression of disapproval, 1801 (n.), 1816 (v.); hence, the verb meaning "shower someone with boos" (1893).

Booing was common late 19c. among London theater audiences and at British political events; In Italy, Parma opera-goers were notorious boo-birds, but the custom seems to have been little-known in America till c. 1910.

To say boo "open one's mouth, speak," originally was to say boo to a goose.
To be able to say Bo! to a goose is to be not quite destitute of courage, to have an inkling of spirit, and was probably in the first instance used of children. A little boy who comes across some geese suddenly will find himself hissed at immediately, and a great demonstration of defiance made by them, but if he can pluck up heart to cry 'bo!' loudly and advance upon them, they will retire defeated. The word 'bo' is clearly selected for the sake of the explosiveness of its first letter and the openness and loudness of its vowel. [Walter W. Skeat, "Cry Bo to a Goose, "Notes and Queries," 4th series vi Sept. 10, 1870]
[boo etymology, boo origin, 英语词源]
deracinate (n.)youdaoicibaDictYouDict
1590s, "to pluck up by the roots," from French déraciner, from Old French desraciner "uproot, dig out, pull up by the roots," from des- (see dis-) + racine "root," from Late Latin radicina, diminutive of Latin radix (see radish). Related: Deracinated.
pluck (n.)youdaoicibaDictYouDict
c. 1400, "act of plucking," from pluck (v.). Meaning "courage, boldness" (1785), originally in pugilism slang, is a figurative use from earlier meaning "heart, viscera" (1610s) as that which is "plucked" from slaughtered livestock. Perhaps influenced by figurative use of the verb in pluck up (one's courage, etc.), attested from c. 1300.
pluck (v.)youdaoicibaDictYouDict
late Old English ploccian, pluccian "pull off, cull," from West Germanic *plokken (cognates: Middle Low German plucken, Middle Dutch plocken, Dutch plukken, Flemish plokken, German pflücken), perhaps from Vulgar Latin *piluccare (source of Old French peluchier, late 12c.; Italian piluccare), a frequentative, ultimately from Latin pilare "pull out hair," from pilus "hair" (see pile (n.3)). But despite the similarities, OED finds difficulties with this and cites gaps in historical evidence. Related: Plucked; plucking.
To pluck a rose, an expression said to be used by women for going to the necessary house, which in the country usually stands in the garden. [F. Grose, "Classical Dictionary of the Vulgar Tongue," 1785]
This euphemistic use is attested from 1610s. To pluck up "summon up" is from c. 1300.