The start of section 8.3 of the venerable The C Programming Language by Brain Kernighan and Dennis Ritchie reads:

Other than the default standard input, output and error, you must explicitly open files in order to read or write them. There are two system calls for this, open and creat [sic].

It is very rare to see [sic] in a text about software because typos in software can be fixed. So why here?

Many UNIX commands are 6 characters or less

If you’ve mucked around in the Linux command line at all, you’ve probably run into this. Why is ‘umount’ not spelled ‘unmount’? is a great SO question that goes into this. The TL;DR is that back in the day, there were real technical limitations on the number of characters that could be used in, for example, file names. In fact, the pdp-11 on which Ken Thomson wrote the original Unix used a character encoding called Radix 50 that could store a maximum of 6 characters in a single machine word. Whether this limitation was real when these system calls were written is unclear, but the practice of using abbreviated words probably persisted.

But wait, creat is only 5 characters. So why drop the ‘e’?

It might actually be a typo

In the 1984 book The UNIX Programming Environment by Brian Kernighan & Rob Pike page 204 the following footnote appears:

Ken Thompson was once asked what he would do differently if he were redesigning the UNIX system. His reply: “I’d spell creat with an e.”

My pure conjecture? Ken Thompson was probably used to thinking up short names for commands. creat was easy - just drop the ‘e’, and he may have not even realized that the full word create would have been only 6 characters.

Redemption?

In 2009 Ken Thompson made this commit to the Go programming language:

spell it with an “e”

All is well that ends well ☺️