1970s; earliest use found in Mattoon (Illinois) Journal Gazette. Shortened from nunchaku (with loss of final vowel probably reflecting partial devoicing of -u in spoken Japanese). Forms with -chuck show alteration after chuck.
To hit (a person or thing) with a nunchuck. Also (in extended use): to fell, defeat, browbeat.
1990s; earliest use found in InfoWorld. From nunchuck.