in cheers, 1870, a shortening of hurrah. Adjective rah-rah is attested from 1907, originally indicating college life generally, later enthusiastic cheerleading.
an early form and later variant spelling of choir (q.v.), Middle English, from Old French quer, queor, variants of cuer, and compare Medieval Latin quorus, variant of chorus.
1874 (Hotten), "pugilist, fighter," agent noun from scrap (v.2). Later used generally of anyone or anything that puts up a fight.