Yi syllable yop

It is one syllable, not a complete word. The standard Latin-letter spelling yop uses final p to mark a low pitch that falls further.

How did Liangshan Yi writing develop?

The standard grew from older, locally varied Yi writing. Bimo, Yi ritual specialists, used earlier forms for religious, magical, medical and family-history texts. Pottery, stone and bronze inscriptions may predate surviving books; the earliest dated example highlighted in standard histories is a bronze-bell inscription from 1485, while paper texts survive from around 1500. The standardized Liangshan repertoire was devised in 1974 and officially promulgated in 1980, adapting Cuan, Wei and local Yi traditions for shared literacy and publishing.