call calf-rope
v. phr.— «“I said I wasn’t going to say anything about the rain, but at this point I am about ready to call calf-rope,” said Kerens Grain’s Sonny Carpenter, using a term meaning, “I give up,” similar to calling “uncle.”» —“Inside the Golden Circle: Rain, rain…“ by Raymond Linex II Corsicana Daily Sun (Texas) June 15, 2007. (source: Double-Tongued Dictionary)
Barry Popik’s web site has several citations for this phrase and some of its variants, here:
http://tinyurl.com/3e37vo
There’s also an entry for it at PBS.org, from their “Do You Speak American?” site:
http://tinyurl.com/yram2k
Thanks! The Dictionary of American Regional English has a full entry for it that takes it back to 1878 and shows that it’s very regional, primarily found in the Gulf states and the South Midlands.