Basketball’s foul line is called the “charity stripe” (or “charity line") because, after a player gets fouled (sometimes with a hard hit), that player gets “charity” shots at the foul line where no one can block the shot. “Charity line” has been cited in print since at least 1922 and “charity stripe” since 1926.
Wiktionary: charity stripe
charity stripe (plural charity stripes)
1. (US, basketball, informal) The free-throw line.
16 December 1922, Springfield (MA) Daily Republican, “Tech Opens the Season By Trouncing Chicopee,” pg. 5, col. 8:
Capt Slate tossed in seven double-deckers and 10 from the charity line.
20 January 1923, Sandusky (OH) Register, “Sandusky Takes First Game From Weakened Fremont Hi Basketeers,” pg. 6, col. 1:
Ebner and Johnson each put one in from the charity line.
7 March 1926, Cleveland (OH) Plain Dealer, “Russell Sets Pace For League Scoring,” pg. 5B, col. 7:
He heads the circuit in tosses from the charity stripe.
3 December 1926, Forest Park (IL) Review, “St. John Buddies in Four Victories,” pg. 8, col. 1:
G. Cote registered three markers from the charity stripe for the Pilgrimites.
2 February 1927, Piqua (OH) Daily Call, “Hosiery Quintet Smother’s Hartzell’s Outfit in the Curtain Raiser at Y. M. C. A. contests,” pg. 6, col. 1:
McKinney hooked Miller and he sunk another from the charity stripe.
16 December 1927, The Evening Repository (Canton, OH), “Mount Union Has Cinch With Kent Normal In Debut,” pg. 49, col. 4:
Burkle led the score with three from action and two from the foul line, while Shafer tailed by a point, having three from the field and one from the charity stripe.
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6 March 1928, Beaver Falls (PA) Tribune, “Keystone Driller Defeats Rossman,” pg. 12, col. 2:
Jack Balph was way off his usual form in shooting fouls in this session, the stocky Rossman forward missing four consecutive tries from the charity line.
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20 December 1934, The Daily News (Ludington, MI), pg. 6, col. 4:
The first period opened with Scottville dropping a basket from the charity stripe.
Pg. 6, col. 5:
Ted Keiser added a basket and Art Wilson contributed a toss from the charity stripe in the first quarter, making the 5 to 2 as the first period ended.
Top 25 Basketball Skills, Tips, and Tricks
By John Albert Torres
Berkeley Heights, NJ: Enslow Publishers
Free throws, or foul shots, are taken from the free-throw line after you are fouled. The free-throw line is also referred to as the “charity stripe,” because no one can guard you while you shoot.