Kirtan comes from the root — kirt, which means to glorify.

HARE KRISHNA
Who is to be glorified in kirtan and for what?
The Bhagavatam answers the first question:
Kaler dosha nidhe rajan, astihi eka mahan guna. Kirtanad eva krishnasya…
That this age is full of so many faults, but there’s simply one good quality left, that is simply by chanting you can become free from material bondage and attain the highest goal in life.
Sometimes there are Ganesh kirtans or Shiva kirtans… but the Bhagavatam says that certainly… eva… Krishna must be glorified.

Kirtancomesroot — kirt,