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]
goose (v.)youdaoicibaDictYouDict
"jab in the rear," c. 1880, from goose (n.), possibly from resemblance of the upturned thumb to a goose's beak, or from the notion of creating nervous excitement. Related: Goosed; goosing. In 19c. theatrical slang, to be goosed meant "to be hissed" (by 1818). A broad range of sexual slang senses historically cluster around goose and gooseberry; goose and duck was rhyming slang for "fuck;" Farmer identifies Winchester goose as "a woman; whence, by implication, the sexual favor," and goose as a verb "to go wenching, to womanize, also to possess a woman." He also has goose-grease for a woman's sexual juices, while gooser and goose's neck meant "the penis." Gooseberries (they are hairy) was "testicles," and gooseberry pudding "a woman."
hiss (v.)youdaoicibaDictYouDict
late 14c., of imitative origin. Johnson wrote, "it is remarkable, that this word cannot be pronounced without making the noise which it signifies." Related: Hissed; hissing.