No, Aristotle did not write about the Druids. There is a 2nd century BC reference by Diogenes Laertius: "There are among the Celtæ and Galatæ those called Druids and Semnotheoi." and he is referring to one of the works of authors known as 'pseudo-Aristotle'.
Nor did Pythagoras. Iamblichus was AD, not BC.
The Druids don't get mentioned until the 2nd century BC.
Doug

Doug Weller

Director The Hall of Ma'at
Doug's Skeptical Archaeology site::
[www.ramtops.co.uk]