Yan over the fence, tan over the fence, tethera over the fence.
Forgive me, I didn't get much sleep last night, so I'm counting sheep. 'Yan Tan Tethera' is the traditional way shepherds from Northern England used to keep an eye their flock. It is a counting system used up until the industrial revolution, with yan standing for 'one', tan for 'two', and 'tethera' for three. It was a ritual performed whener the flock was moved or sheared to make sure none of the sheep went missing.
In popular culture, the term has been referenced in both books and music, particularly ones featuring folk traditions. David Littler from the English Folk Dance and Song Society has curated a special Yan Tan Tether Season for Cecil Sharp House, in which there will be various activities starting from the 10th May. These include an exhibition, festival, and workshops.