SOCIETY FOR CONSTITUTIONAL INFORMATION: Owen McDermott Esq of Delahay St, Westminster proposed member 31.10.1788 by Joseph Adams 2nded Thomas Brand Hollis
William McDermott son of Owen McDermott of Galway admitted Trinity College Dublin 1815 age 17, admitted Grays Inn 1828 son of Owen McDermott of Springfield, Galway. William McDermott of Springfield died 1877. William Kelly of Springfield House had had two daus who married Owen McDermott and Glasgow Connolly (landedestates.nuigalway.ie). Owen McDermott =1791 Honora Kelly. Owen McDermott subscr 1791 to Reports of Cases Kings Bench Dublin. 1793 Owen McDermott secretary of Dublin Society of United Irishmen, died 1825. "Attorney Owen McDermott, brother of the Colonel Thomas McDermot Roe of Emla who died in the French Revolution" was the secretary of Dublin chapter of United irishmen (irishmasonichistory.com/laurence-dermott-freemasonry-and-the-macdermotts). "The Irish Emigrant" 1817 anon was a novel about an United Irishman called Owen McDermott. The brother Thomas, Colonel of a Roscommon militia regiment, joined Lord Edward Fitzgerald in Paris and died in the Temple prison in 1793 (wikipedia Mac Dermot Roe). The brothers were perhaps sons of Edmund MacDermott of Emlagh who married Elinor Kelly and died 1778, and he was perhaps the son of Thomas McDermott of Cashelmeehan. An Owen McDermott son of John of Coot Hall, Roscommon was admitted to the Middle Temple 15.5.1756. An Owen McDermott married at St James Piccadilly 12.5.1764 Mary McNolty. There was an Anthony McDermott of Coote Hall 1768 (National Library of Ireland MS 48,361/22). An Owen McDermott, tried in Dublin in 1800 was transported to New South Wales on the Atlas II and took part in the Castle Hill rebellion of 1804 (Unfinished Revolution by Anne-Maree Whitaker). An Owen MacDermott married at St Pancras 1.9.1805 Mary Hearn. I'm afraid I can't identify any of these people with much certainty yet