forthwith

The story

1. Middle English · inherited fromforth-with“at once, immediately; at the same time, already; straight ahead”
2. English todayforthwith

From Middle English forth-with (“at once, immediately; at the same time, already; straight ahead”) [and other forms], partly from the phrase forth with (something), and partly from forth-with-al, furth-with-al (“at once, immediately; together with”) (whence forthwithal).

First known use, by meaning

• from early 14th c. Without delay; immediately.