Learning a new language is difficult for adults. Unlike children's brains, your brain has more difficulty absorbing the tones and rules of a new language. Tonal languages can confuse those unfamiliar because how you say a word changes meaning.
So, let me set the stage. I'm an Australian who scored a sweet gig working at a resort on a tropical island in Thailand. I had 50 awesome staff members working under me, and, wanting to make a great impression; I took the time to learn everyone's names, both their formal and nicknames.
Now, here's where the colossal screw-up comes in. One of my staff members had the nickname Moaj, which I was told meant 'China girl.'
Eager to be friendly and relatable, I called her by her nickname for three years. Little did I know, I was calling her 'pubic hair' due to the nuances of the Thai tonal language.
For three long years, I unknowingly called this poor woman an NSFW name, and nobody corrected me. Finally, one staff member let the truth slip, and I was mortified.
I had been walking around, blissfully unaware of the embarrassment I had been causing both myself and Moaj. To say I was devastated is an understatement.
TIFU big time by not fully understanding the tonal intricacies of the Thai language and accidentally calling my employee a wildly inappropriate name for years. Learn from my mistake, folks. When in doubt, stick to formal names.
The internet also has trouble with new languages.
I work with many Mexicans, and the words load and sh*t are very similar. I was telling the guys to go sh*t in the truck instead of go load the truck for five years! Until a new guy came and pulled me aside and explained how I was pronouncing it wrong.
I turned to the rest of the crew 'WHY DIDN'T YOU GUYS TELL ME?!' To a chorus of laughter from them, 'Well we always knew what you meant.' I wanted to die.
To be fair, nobody, including her, told you. Honestly it sounds more like a prank on you to let that run that long unless there's a whole lot of other f*ckey sh*t going on.
Same situation here. I've been living/working in Thailand for eleven years. For the first five I was calling one of my team, who's name is Koi, 'Koi' as in the fish. It's actually pronounced 'Goi.' 'Koi' means penis in Thai, or more specifically, slang for 'cock'. So yeah.
OP, I think your employees were just hazing you into their culture.