"Don’t knock it ‘til you’ve tried it” is something someone might say to another to get that person to try a new product. “Don’t knock it ‘til you’ve tried it” was cited in print in 1940 and “Don’t knock it until you’ve tried it” was cited in 1953. The saying was cited frequently in the 1950s.
The New York City-inspired television series Naked City had an episode titled “Don’t knock it till you’ve tried it” on December 26, 1962.
15 March 1940, Wisconsin State Journal (Madison, WI), pg. 15, col. 2:
Freddie’s “don’t knock it ‘til you’ve tried it” remark to package-wrapper Mamie in the taxi.
27 March 1953, Lubbock (TX) Evening Journal, “Actress Gets First Big Role With Martin and Lewis” by Aline Mosby (UP), sec. 2, pg. 5, col. 4:
“Don’t knock it until you’ve tried it,” she added firmly.
Google News Archive
3 January 1955, St. Joseph (MO) Gazette, pg. 4, col. 6:
The fellow at the next desk says he feels about peaceful co-existence the way he does about an improbable-sounding recipe on the women’s page—until you’ve tried it, don’t knock it.
30 June 1956, Greensboro (NC) Record, “Inside TV” by Eve Starr, pg. A-8, col. 7:
He comes of a sound school of thought: “If you haven’t tried it, don’t knock it.”
OCLC WorldCat record
The naked city. Don’t knock it till you’ve tried it
Author: Alex March; Charles Russell; Paul Burke; Horace MacMahon; Harry Bellaver
Publisher: United States : ABC-TV, 1962-12-26.
Edition/Format: Film Visual material : English
25 July 1965, Seattle (WA) Times, “With Shoes Reversed: Elation Romps Off With Everett Purse” by Bob Schwartzmann, fourth sec., pg. 35, col. 6:
Don’t knock it if you haven’t tried it.
It’s Your Life So, Take Your Choice
Glendale, CA: G/L Regal Books
Unfortunately, there are people who agree with Ringo’s limited logic. Don’t knock it before you really try Him.
OCLC WorldCat record
Self-Help Literature: Don’t Knock It Till You Try It
Author: Josiah Dilley
Edition/Format: Article : English
Publication: The Personnel and Guidance Journal, v56 n5 (19780103): 293-295