英语词源字典 - 在线词源网站

ball (n.2)[ball 词源字典]: "dancing party," 1630s, from French, from Old French baller "to dance," from Late Latin ballare "to dance," from Greek ballizein "to dance, jump about" (see ballistics). Hence, "very enjoyable time," 1945, American English slang, perhaps back to 1930s in black slang.[ball etymology, ball origin, 英语词源]
hop (n.3): "a small jump," c. 1500, from hop (v.). Slang sense of "informal dancing party" is from 1731 (defined by Johnson as "a place where meaner people dance"). Meaning "short flight on an aircraft" is from 1909.