Ireland: The A-Z Irish Glossary - 'O' is for 'One'
'One'
Apart from being the title of a very beautiful and popular U2 song, to Irish (particularly Dublin people) it is often pronounced "wan" and refers to a person of the female sex. Usually qualified, e.g. "young one" or "oul' one".
Note the use of the article: "A young one" or "An oul' one" can refer to any young or old female of the speaker's acquaintance, but "the young one" refers to the speaker's girlfriend or daughter, while "the oul' one" refers to his wife or his or her mother.
This is a common feature of Irish speech, using "the" rather than a possessive pronoun like "my" or "your". "How's the brother?" "He's grand, but the sister has me tormented."
A perfect demonstration of this type of phrasing can be found in well-known actor/comic Brendan O'Carroll's book "The Young Wan".