In computing, grist is the addition of characters before and/or after a parameter to ensure uniqueness to a software interpreter. For example, in a UNIX shell if there is a file named "-f" in the current directory, the following command:
> rm -f
Will not work because "-f" is interpreted as an option to the "rm" command. Rather, one needs to "add grist" to get the appropriate behavior:
> rm ./-f
In this case, "./" is grist because it prevents "-f" from being interpreted as an option.
In popular culture
In the series Homestuck by Andrew Hussie, a material called grist exists a fundamental material in the computer simulation-like world in which the work is set.
References
Grist (computing) Wikipedia(Text) CC BY-SA