Wasei-eigo from 'pendant top'; refers specifically to the decorative part of a pendant, not the chain.
wasei-eigo (Japanese-coined English), from pendant top
このペンダントトップは手作りです。
This pendant is handmade.
チェーンは別売りで、ペンダントトップだけを購入しました。
The chain is sold separately; I bought only the pendant.
Variant with interpunct; less common in everyday writing.
Wasei-eigo from English 'pendant top', referring to the decorative part of a pendant necklace.