I will narrate an incident that happened couple of months back when I was in Bangalore. One morning, the phone rang and I answered the call. The gentleman on the phone was my dad's colleague and wanted to talk to my dad. As my dad was away in the restroom, I politely told him that dad is in the restroom and he will call back soon. To my surprise, the gentleman asked me
"Is he sleeping?".. What does he mean.. sleeping and that too in the restroom of all the other places..
I realised that I should have used the most (decent!) word of toilet instead of restroom. As the gentleman is in a top position in a top organisation, I used the word restroom as I thought he would know the meaning of the same. So, that indicates that I should not boast too much of the little bit decent English that I know and use beginners' language itself!!