pygostyle
The plate supporting the tail-feathers in birds, formed from fused vertebrae.
Aderyn the Bird Queen sat down; her pygostyle engaged a hard wooden bottom.
Where it comes from
From English pygo- + Ancient Greek στῦλος (stûlos, “column”). By surface analysis, pygo- + -style.
Adapted from the Wiktionary entry pygostyle (CC BY-SA 4.0).