cockle-burr vs cockle-bur

cockle-burr and cockle-bur both are nouns.

Word	Noun	Adjective	Verb	Adverb
cockle-burr	Yes	No	No	No
cockle-bur	Yes	No	No	No

As nouns, cockle-burr and cockle-bur are synonyms defined as:

cockle-burr and cockle-bur: any coarse weed of the genus Xanthium having spiny burrs

Other synonyms of cockle-burr include cocklebur, cockleburr.

cockle-burr (noun)	cockle-bur (noun)
any coarse weed of the genus Xanthium having spiny burrs	any coarse weed of the genus Xanthium having spiny burrs