deformity of the thorax (Billings, 1890). [ < thoraco-comb. form + ancient Greek κύλλωσις condition of club foot ( < κύλλοῦν to crook, flex ( < κυλλός deformed, crippled, crooked, of uncertain origin) + -σις-sissuffix), after scientific Latin thoracocyllosis (1839 or earlier).]