I noticed that in Italian usually there is only one gender for one word, but there are some exceptions I thought were because of "bad native speakers". One of this exception is "tavolo" / "tavola". What's the explanation and the etymology behind this divergence?
"Tavolo" is table as the furniture item. "Tavola" has (at least?) two separate meanings: a table set to eat, and "board". The etymology is actually the same, from the latin tabula.
I'm looking for some concrete info on when "tavolo" and "tavola" did split from the common ancestor, but so far I found zilch (0) info, sorry. Treccani in "Alternanza di genere e significato" just comments
"A volte l’alternanza non produce sostanziali cambiamenti di significato, ma dà origine soltanto a diverse sfumature"
which translates to "Sometimes the gender switch does not result in a substantial change in meaning, but just originates nuances." - and that's as far as I could go, sorry.