Onn, meaning gorse, is the 17th letter of the ogham alphabet. It equates to the English letter O.
Gorse is often associated with love and fertility. It was for this
reason that a sprig of gorse was traditionally added to a bride’s
bouquet and gorse torches were ritually burned around livestock to
protect against sterility. However, one should never give gorse flowers
to another as a gift for it is unlucky for both the giver and receiver.
In Celtic tradition, gorse was one of the sacred woods burned on the
Beltane bonfires, probably the one that got them started. It was a shrub
associated with the spring equinox and the Celtic god of light, Lugh,
doubtlessly because of its ever blooming vibrant yellow flowers.