Lat. "Arbor"

Hello everyone,

could somebody possibly help me with the etymology of Lat. "arbor", please?

This is what Pokorny says:

Proto-IE: *arbh- ?

Germanic: *arb-ō(n-) f. > German: Arbe, Arfe `Pinus cembra'

Latin: arbor / arbo:s, -oris f. `Baum'; arbutus, -i: f. `Hagapfelbaum, Erdbeerbaum, Arbutus unedo L.'