All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
There is no sin in using this word or any other word in greeting and welcoming as long as it does not indicate a meaning that is contrary to the Sharee’ah.
If we presume that what you mentioned is true, that it was used originally in the sense of ‘I am your slave’, then what is considered and important is the meaning of the word according to people's usage, regardless of its origin.
We advise you to repel these whispers, ignore them, and seek to treat them.
Allah Knows best.