I was just listening to some Mongolian and it struck me that the word for "language", хэл, is quite similar to the Estonian word for "language", keel.
I know it's not accepted that these languages are related, but some linguists accept various hypotheses that they are, along with Turkic, Japonic, Korean, etc.
I'm also aware that coincidences are especially common in single-syllable words.
However I'm interested to know if anyone remotely credible includes these terms in their higher-order protolanguage reconstructions, etc.
Conversely I'd be interested to see if known sound changes in these languages/families rule out any relationship.