thrush, (kokuji)
𪃹 is a kokuji (Japanese-made kanji) that refers specifically to a thrush, a type of bird. Its meaning is narrow and concrete, with no broader conceptual extensions.
𪃹 is a kokuji, likely created in Japan by combining 鳥 (bird) with a phonetic or semantic element to represent a specific bird species. The exact historical development is uncertain, but it follows the common pattern of bird-related kokuji.
The right side is 鳥 (bird), and the left side looks like a complex perch or branch. Picture a thrush sitting on that perch, singing its distinctive song.
For じない, imagine a thrush named 'Jinai' that always returns to the same branch: Jinai -> じない, and the bird's name helps you remember the reading.