The sentence "Rose is a rose is a rose is a rose." was written by Gertrude Stein as part of the 1913 poem Sacred Emily, which appeared in the 1922 book Geography and Plays. In that poem, the first "Rose" is the name of a person. Stein later used variations on the sentence in other writings, and "A rose is a rose is a rose" is probably her most famous quotation, often interpreted as meaning "things are what they are", a statement of the law of identity, "A is A".
The sentence was parodied by Ernest Hemingway after a brief time in Paris seeking editorial suggestions for his writing: "a stone is a stein is a rock is a boulder is a pebble." This also appears in his 1940 novel For Whom the Bell Tolls, in which there is yet another parody: "a rose is a rose is an onion." After a (perhaps bitter) falling out, the sentence becomes, "a bitch is a bitch is a bitch is a bitch."