así
/aˈsi/ · A1 · adv
so
a + sí: Latin ad sic, sic meaning thus — the same sic as in [sic]
Así comes from Latin sic (thus, so), the same word editors write as [sic] to say it was written just like this. Spanish sí (yes) also comes from sic, so así is roughly a + sí: yes, like so, in this way.