I know that "Saavi" is a loan word but I don't remember which language it is from. Portuguese?? may be.
The old tamil word for key is "Thiravu Kol" (திறவு கோல்). I heard that my great grandparents used to use the word "Thorappu Kuchi" (தொறப்பு குச்சி) for key in Kongu Tamil. In Palakkad Tamil, they use the word "Thaa Kol" (தாக்கோல்) which is a colloquial version of "thiravu kol".
Currently "Saavi" has replaced all the other usages.
There is another Portuguese loan word "alamari" (அலமாரி) which is from Portuguese armário (Almirah)