Sabine wrote:
"Aren't you confusing a couple of roots? The Goidelic adverbs meaning 'in
front', 'behind', 'left' and 'right' (OIr air,
íar, túaid, dess) also
designate the four directions (E, W, N, S) as viewed by an
observer facing the rising sun. This accounts for the north/left
connection, while the association of 'left' with 'bad' is an anatomically
grounded universal.
The root *teut-, which underlies Old Irish
túath has nothing to do with 'left' or 'north', or 'evil' for
that matter."
Though they look the same, Tuath ("tribe") and Tuaith ("north") are
from two separate roots - check it for yourself in Pokorny's
IEW