O is for Onions

mature like Italian
(also Spanish and shallot)
or youthful like scallion.

open shop
ontology -- existence/being
onomatopoeia
oxgang - bovate
itiose
on the shelf - has been
onus probandi - obligation of proof
Osages
Osier
Ossining
Osman
Og King of Bashan
obicular - leaf shaped
oriflamme
overlapping debt
oste
obi
oligopsony
overhead costs
outre
oneiromancy
occlusive