"Chandra" [चन्द्र] is one of the Hindi/Sanskrit words for the Moon. Other examples are chaand and chandni.

"Yaan" [यान] means vehicle/coach.

That would be Chandraayan: moon + journey/path. Chandrayaan is moon + vehicle.

Chandraayana would mean "Journey by/to the moon" as in Ramayana or Uttarayana.

Chandrayaana means moon vehicle.

The thing that annoys me is that ISRO uses Hindi naming convention rather than the Sanskrit. Visarga is a thing.

Chandrayatra means journey to moon.