Paan or pan is a preparation of betel leaves and other ingredients which is chewed as a stimulant. It's quite buzzy. It also stains your mouth red.
Hindi पान pān is from Sanskrit पर्ण parṇa "feather, leaf" (OED) from PIE *por-no- "that which carries a bird in flight" (possibly). From the same PIE form is English fern, so called because it has feathery fronds.
*por-no- is a suffixed o-grade form of *per- "lead, pass over".