The name "Guinness" is derived from "Mag Aongus" meaning son of Aongus who in mythology was a member of the Tuatha Dé Danann and probably a god of love, youth and poetic inspiration. Aon = one and gus = choice thus literally meaning one choice but more accurately translated as 'chosen one'. In Irish orthography "Mac" meaning "son of" changes to "Mag" when the following name begins with a vowel. When the name is vocalised in speech it sounds like Ma'gaon-gus or ma'gan-gus which in turn is phonetically rendered to English as MacGuinness. During the 17th century under pressure from the English authorities many Irish families dropped the prefix "Mac" to make their name sound more "English".
In 1518 a town statute declared "Neither O nor Mac shall strut nor swagger through the streets of Galway."
Consequent of such pressures, the use of Mac and O’ was dropped by many families. Although some families have since revived the O or Mac, while others never did. This explains variations in surnames like Mahony and O’Mahony, Neill and O’Neill but each variant has a common history.
Many old Gaelic names became Anglicised. Sometimes the Anglicised version was a translation, sometimes a phonetic spelling of the Irish, sometimes a mixture of the two.
The proprietor of the Guinness brewery Benjamin Lee Guinness chose the
harp motif in 1862 and registered is a a trademark shortly after the
passing of the Trade Marks Registration Act of 1875. Could Benjamin's
choice of logo have come from the Aongus stories who had a harp that
made irresistible music and his kisses turned into birds that carried
messages of love.
Certainly Guinness (the product) is irresistible to some and without it (I surmise) many would not have been able to find love!