the twelfth letter of the Irish alphabet, stood second in the
vowel-group of the Ogham alphabet and was known by the
name onn `furze' (? `ash').
O.Ir. ŏ in accented syllables generally represents Indogerm.
o. In declension it freq. interchanges with u according to the
nature of the vowel in the syll. originally following: mug, g
moga; sruth, gs. srotha; cú, gs. con. In Mid.Ir. o often > a:
bos(s), bas(s) `hand'; for `your', far; fota `long', mod. fada;
goba, gaba `smith' (O.Ir. d
s. gobaind); ocus `and', acus, mod.
agus. In bardic poetry o and a are freq. interchanged to
secure rhyme; fola `grudge' beside fala; rogu `choice' beside
O.Ir. ō generally results from the contraction of an orig.
diphth. au, eu, or ou. Later it freq. gives way to the diphth.
ua: ó, úa `grandson'; lóg, lúach `price'; slóg, slúag `host';
tróg, Mid.Ir. trúag `wretched'.
In Latin loan-words o generally remains (corn, corp < Lat.
cornu, corpus); ō becomes ó, later ua (hóre, (h)úare, úaire <
Lat. hōra); au also gives ó (ór, Pól < Lat. aurum, Paulus).
In Irish notation o also appears in combination with a
follg. vowel: (a) oi (palatal o), denoted in the Ogham alphabet
by a single character called oir `spindle-tree'. In Mid.Ir. oi is
freq. replaced by ai (esp. after f, see
Thurn. Hdb. 77
`pigsty', later fail; fairend, foirenn `company', O.Ir. foirinn,
; foil(l)sigid `makes manifest', failsigid; O.Ir. clainde
gs. of cland `children', Mid.Ir. clainne, cloinne; glaine `purity',
). Conversely orig. ai is somet. replaced by
oi; Mid. oile `other' beside aile; ail `blame', later oil; oire
`burden' beside aire. Such changes are freq. in bardic poetry.
(b) ói = palatal ō. (c) oí (diphth.) in Mid.Ir. generally oe, ae,
mod. ao, aoi (a single vowel-sound); O.Ir. noíb, Mid.Ir. noeb
(noem), naeb (naem), mod. naomh. The diphths. oí and aí
freq. fall together: áis `people',
; táis `dough',
; see also oí `sheep', oíbell,