If you're reading this into R using readxl::read_excel(), it will by default try to convert your object into a data frame (more specifically a tibble — you can tell what the return object will be by looking at the value in a function reference).
So, what's happening is that readxl is attempting name repair, and giving your columns names, rather than keeping it as a matrix:
You can read your sheet in from a csv and convert it to a matrix, or read it in as an Excel file and do the same. See this thread on Stack Overflow:
If you need further assistance, could you please turn this into a self-contained reprex (short for reproducible example)? It will help us help you if we can be sure we're all working with/looking at the same stuff.
install.packages("reprex")
If you've never heard of a reprex before, you might want to start by reading the tidyverse.org help page. The reprex dos and don'ts are also useful.
What to do if you run into clipboard problems
If you run into problems with access to your clipboard, you can specify an outfile for the reprex, and then copy and paste the contents into the forum.
reprex::reprex(input = "fruits_stringdist.R", outfile = "fruits_stringdist.md")
For pointers specific to the community site, check out the reprex FAQ.