The Seonaidh wis a watter speerit in Lewis, bi the wey o Martin Martin.[1]
Dwelly pits seonadh (wioot the "i", a relatit form in Scots Gaelic) as "1. augury, sorcery. 2. Druidism" an quotes frae Martin further.
Martin says thit the fowk thit bade in Lewis uised tae gain favour o Seonaidh bi a cup o ale in the followaein weys, in a ceremony thit wis, for ordinar, duin at nicht. They came tae the kirk o St. Mulway (Mael rubha), ivery man cairyin his ain fuids an drinks. Ivery faimilie gied a poke o malt, an the hale wis brewed intae ale. Ae o thaim wis chysen tae wawk intae the sea up tae his mids, cairyin a cup fou o ale in his haund. Whan he got tae a proper depth, he stuid an cried lood oot:
(in Inglis) Seonaidh, I give thee this cup of ale, hoping that thou wilt be so good as to send us plenty of seaware [seaweed used as a fertilizer] for enriching our ground during the coming year.
He thrawn the ale intae the sea efter. Thay than won back tae the kirk, whaur thare wad be a caunle burnin at the altar, thit, efter a seegnal, wad be pit oot. Efter a while, thay went tae the fields an celebrate wi the ale remainin. The nixt mornin, thay wad gae back tae thair hames.
Thay believed thit gin thay did this, it wad gie thaim a muckle crop fur the nixt season.[2]
It seems likely thit Seonaidh wis some kind o god tae stairt wi, thit's worship haed been lichtly Christianised bi eikin on sindry kirk featurs. Hounaiver, it's possible thit Seonaidh, the Scots Gaelic form o the English an Scots Johnny, micht be a reference tae ae o the Saints John an aw.