Lead singer Fish was born in Dalkeith, a town in the county of Midlothian, Scotland just outside Edinburgh. Lothian is a district in Scotland and Midlothian is the middle part of it. The Royal Mile, which is also referred to in the song, is the main High Street in Edinburgh. There is a heart-shaped mosaic embedded into the pavement halfway up the Royal Mile in Edinburgh. The heart is traditionally a symbol of local pride. One of the Edinburgh football teams is known as Heart of Midlothian, or "Hearts" for short.
Fish, like most Scots, is very proud of his county and saying that he was born with a Heart of Lothian is an echo of this local pride and nationalism.
The song is split into two parts, firstly "Wideboys," where Fish recalls fondly of when he was one of the wide boys, a term for teenagers spending all their cash in watering halls (pubs) as if they will never run out of money. In the second part, known as "Curtain Call," he is back in reality, wondering how he ended up in his current lifestyle, wanting to return to his old adolescent life, back to the waterhole.
Sir Walter Scott also wrote a book called The Heart of Lothian in 1818 and in this case the title of the book refers to the Old Tolbooth Prison in Edinburgh.