How to suppress automatic table name and number in an .Rmd file using xtable or knitr::kable?

It turns out that I needed to add the following in the YAML section:

header-includes:
    - \usepackage{caption}

AND the following somewhere before the code chunk:

\captionsetup[table]{labelformat=empty}

Now it works:

---
title: "Suppress automatic table name and number"
output: pdf_document
header-includes:
    - \usepackage{caption}
---

\captionsetup[table]{labelformat=empty}

```{r myirischunk, results = 'asis', tab.cap = NULL, echo = TRUE}
print(knitr::kable(head(iris), caption = "Table 21.a - My very own table name"))
```

This has also been described here:

Get rid of captions using texreg in markdown

And yes, I'm a bit embarrased that I didn't find that answer straight away.

Anyway, thanks to daroczig for pointing me in the tex direction instead of trying to solve the problem using chunk options or something like that.

In case you also want figures the same way, modify the example by vestland to

---
title: "Suppress automatic table name and number"
output: pdf_document
header-includes:
    - \usepackage[labelformat=empty]{caption}
---

and skip the \captionsetup{}.