A single word can have different meanings. If “hello” means “go to hell” as you have said in your question, it is also used to welcome others. Thus, if anyone says “hello” to welcome others, it is permissible. There is no harm in it.
One should not use this word in the wrong sense. It is necessary to refrain from doing so.
And Allah Most High knows best.
Mufti Syed Ziauddin Naqshbandi Qadri
[Professor, Islamic Law, Jamia Nizamia,
Founder-Director, Abul Hasanaat Islamic Research Center]