/bin/sh, i.e. the Bourne shell, has been written by a programmer who was experienced in ALGOL 68, having implemented some significant projects in it.

In designing the language interpreted by the shell, he has taken several features directly from ALGOL 68.

However he has also done one improvement, renaming the bracket pair keywords "do" and "od" to "do" and "done", responding thus to the criticism of many programmers towards ALGOL 68, that "od" sounds odd.

In particular, one of the projects that Steve Bourne had previously done is the Algol68C compiler at Cambridge. See: https://www.softwarepreservation.org/projects/ALGOL/algol68i...

Steve Bourne wanted to use od to end loops in his shell but was prevented because od was already the octal dump program.

And as other HN commenters have noted recently, Bourne used #define to make the shell source code look like Algol:

https://research.swtch.com/shmacro