Green’s Dictionary of Slang

(US, Western) to shy, to panic, usu. of an animal.

1893		H.A. Shands Speech of Mississippi 70: Booger [...] The word is used also, by illiterate whites, as a verb, meaning to shy, to get slightly frightened, and is said of a horse [DARE].
1903		S. Clapin New Dict. Americanisms.
1905		J.W. Carr ‘Words from Northwest Arkansas’ in DN III:i 71: booger, v. ‘He boogers’ Used of a skittish horse.
1952		F.C. Brown North Carolina Folklore 1 521: Booger at [...] To start at from fright (?) [...] ‘The horse kinda boogered at him.’.
1970		in DARE.
1999		‘Lance Howard’ Deadly Doves Ch. i: Dull panic crept into Whip’s mind and his heart stuttered. He wasn’t sure at first what boogered him, but even with half his spurs jangling he knew something was wrong. Puredee bad wrong.
2000		‘Lance Howard’ Devil’s Peacemaker Ch. i: The words came out almost a whisper and Cyrus wasn’t proud of it. He had never backed down to any man or beast in near to seventy years, but something about this fella plain boogered him.
2004		L.J. Hunt Abernathy Boys 66: This boogered him terribly. The horse reared and screeched and nearly threw Temp backward out of the saddle.