Hi, just looked it up in Barbara Brackman's Ency. of Pieced Quilt Patterns, and it first appeared unnamed in 1875. Other names it went by: Always Friends; Spools; Friendship Chain, Badge of Friendship; Double Ax; Jigsaw; Charm; Friendship Quilt; Mother's Oddity. Curiously, BB doesn't mention "Apple Core" for any pattern. It is not listed in the Index. Happy Quilting!