Guru is actually a Sanskrit word. Sanskrit is an ancient Indian Language.
Guru is derived from two roots Gu and Ru.
Gu means darkness and
Ru means to dispell it.
So guru is someone who dispells the darkness.
Now if I go deeper into it I'd say darkness is the absence of light...
I think I'd better stop it here...
He who takes you from the absence of light (knowledge) to light is your guru.
Put it simply a guru is a teacher who teaches not just conveys
It is a beautiful word and I love it...
Have a great day