I recall a story of a fellow interpreter when he was guiding an English-speaking group in a botanical park and came up to an evergreen plant of a box-tree. The word was rare and not in the active vocabulary. So, thinking that it may be some derivative of Latin he had settled his mind to use a Russian equivalent ('And here my dear Ladies & Gents we can see...') with the hope that the English-speakers would understand. And they did understand indeed. In Russian, a box-tree is called, sorry, самшит (sʌm ˈʃɪt). Curtains.

I don’t remember if there were any words I found funny when I began to learn English - it’s a long time ago.
But “crab apple” sounds funny to me, because it sounds almost like ”crap apple”.

And to me it's funny that "source" and "sauce" are homophones the way I pronounce them (I speak with a non-rhotic Received Pronunciation influenced accent). At times it's hard for me not to think of sauce when I think of a sentence with "source":

"His sources are unreliable."

"It's a great source of happiness."