"excellent person or thing," 1897, a sense extended from coveted varieties of apple that were raised from seed (so called since late 14c.), from Middle English pipin "seed of certain fruits" (see pip (n.1)).
Entries linking to pippin
pip n.1
1797, "seed of an apple (or orange)," a shortened form of pipin "seed of a fleshy fruit" (early 14c.), from Old French pepin (13c.), probably from a root *pipp-, expressing smallness (compare Italian pippolo, Spanish pepita "seed, kernel").