acrostic waka with hidden name
A classical waka form where the initial morae of each line spell out a hidden word, often a plant, animal, or place name. Primarily a literary and historical term.
The Kokin Wakashū contains several acrostic poems with hidden names.
From 物名 (thing name) + 歌 (poem). The exact historical origin is uncertain, but the form appears in classical Heian-period anthologies.