Why does Postgres ORDER BY seem to halfway ignore leading underscores?

I have an animal table with a name varchar(255), and I've added rows with the following values: Piranha __Starts With 2 Rhino Starts With 1 0_Zebra _Starts With 1 Antelope _Starts With 1 When I run this query: zoology=# SELECT name FROM animal ORDER BY name; name ----------------- 0_Zebra Antelope Piranha Rhino _Starts With 1 _Starts With 1 Starts With 1 __Starts With 2 (8 rows) Notice how the rows are sorted in an order that implies the leading _ is used to place the _Starts With 1 rows before the Starts row, but the __ in the __Starts With 2 seems to ignore this fact, as if the 2 at the end is more important than the first two characters. Why is this? If I sort with Python, the result is: In : for animal in sorted(animals): ....: print animal ....: 0_Zebra Antelope Piranha Rhino Starts With 1 _Starts With 1 _Starts With 1 __Starts With 2 Furthermore, Python ordering suggests that underscores come *after* letters, which indicates that the Postgres's sorting of the first two _Starts rows before the Starts row is incorrect. Note: I'm using Postgres 9.1.15 Here are my attempts at finding the collation: zoology=# select datname, datcollate from pg_database; datname | datcollate -----------+------------- template0 | en_US.UTF-8 postgres | en_US.UTF-8 template1 | en_US.UTF-8 zoology | en_US.UTF-8 (4 rows) And: zoology=# select table_schema, table_name, column_name, collation_name from information_schema.columns where collation_name is not null order by table_schema, table_name, ordinal_position; table_schema | table_name | column_name | collation_name --------------+------------+-------------+---------------- (0 rows)