what is it popular for?
Mountaineering.
Old Man of Hoy
The stack was first climbed by mountaineers Chris Bonington, Rusty Baillie and Tom Patey in 1966. From 8–9 July 1967, an ascent featured in "The Great Climb", a live BBC three-night outside broadcast, which had around 15 million viewers. This featured three pairs of climbers: Bonington and Patey repeated their original route, whilst two new lines were climbed by Joe Brown and Ian McNaught-Davis and by Pete Crew and Dougal Haston.

where did the old man of hoy get its name It is a sea stack on Hoy, part of the Orkney archipelago off the north coast of Scotland.
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Old Man of Hoy [SEP] Climbing
The stack was first climbed by mountaineers Chris Bonington, Rusty Baillie and Tom Patey in 1966. From 8–9 July 1967, an ascent featured in "The Great Climb", a live BBC three-night outside broadcast, which had around 15 million viewers. This featured three pairs of climbers: Bonington and Patey repeated their original route, whilst two new lines were climbed by Joe Brown and Ian McNaught-Davis and by Pete Crew and Dougal Haston. In 1998, Catherine Destivelle was the first person to make a solo ascent of the Old Man of Hoy; she did so while four months pregnant. Red Széll became the first blind person to climb the Old Man, despite suffering from retinitis pigmentosa that left him with 5% vision.