Kenne aus dem AE "Charley horse" auch nur als Krampf, Muskelkater dagegen as "sore muscles". Zwei weiter Woerterbuecher geben im Aggregat jedoch beide Bedeutungen an.
Lighter, Historical Dictionary of American Slang:
Charley horse n. [see note] 1. Orig. Baseball. A cramp in an arm or leg muscle resulting from excessive strain or from a blow. Now S.E. [Despite investigation, the origin of the term remains obscure.]
1888 in AS (1949) XXIV 103: I could dance in those days, because, you see, I never was bothered with "Charley Horse"
1889 in DA
1908 in Fleming Unforgettable Season 74: Ball players get charley horses of the legs, but umpires can get the same charley horse in the head
Dictionary of American Regional English:
Charley horse n [Orig uncertain: see 1949 AmSp 24. 100-104]
widespread, but least freq NEast and Sth
A pain or soreness, usu in a muscle and often the result of a bruise
1888 in 1949 AmSp 24. 103, I could dance in those days, because, you see, I never was bothered with "Charley Horse"
1913 Amer. Mag. July 68/1 West, Everybody got jov'al, and the barkeep at Sierra Joe's got a charley-horse tryin' to keep up with his orders
1965-1970 DARE (Qy. BB4, .. A pain .. "He's had a ____ in his arm for a week.") 42 Infs [...]