Yam is the seed of anahata, the heart center, assigned to air in the same 1577 compilation, Purnananda Yati's Shat chakra nirupana, that fixes the whole six chakra scheme used across these entries. Anahata's twelve petalled lotus and its name, unstruck, describing a sound produced without two things colliding, are part of Purnananda's elaboration, and the idea of an unstruck sound at the heart draws on an older Nada Yoga concept of subtle, self arising sound current in earlier Tantric and Yogic material, so the chakra's name preserves an older idea even where its placement in a six part map is the sixteenth century text's own contribution.
Translation and transmission here run into a genuinely unresolved dispute among scholars of Tantra over what a bija actually denotes linguistically. One school treats yam and the other chakra seeds as acoustically motivated, sounds whose phonetic qualities are held to resonate with the element or quality they represent, air's association with yam reasoned from the semi vowel's light, breathy articulation. A rival, more historically grounded position, associated with several twentieth century Indologists working on the Tantric alphabet systems called the matrikas, argues that bija assignments follow a formal alphabetic scheme, an ordered mapping of Sanskrit's phonemes onto ritual categories, rather than any perceived acoustic resemblance, so that yam's connection to air is systemic rather than sonic. Neither camp has produced decisive evidence, and popular yoga literature typically presents the acoustic explanation as settled fact when it is one contested reading among specialists.