This tune was written by Cambridge NY fiddler Stephan Deibel. It was originally titled "Seals and Sky" and was written September 2015 on Janvrin's Island, a place with many seals and much sky that is off Isle Madam in the southeast corner of Cape Breton. The tune was later retitled to better match its character.
This reel was the first tune ever written by Shetland fiddler Samuel Ian Rothmar Burns, probably around 1960. Spootiskerry is the name of a farm in the author's family. In his tunebook, also called Spootiskerry, he says "Spootiskerry [is] the croft belonging to my late grand aunts, Bella and Joan Nicolson, situated between the village of Sullom, and the new town of Brae." A spoot is a razor clam, one of the edible "ebb meats" taken from the shore at low tide, named because it "spoots" (or spouts) when you disturb it. A skerry is a group of rocks which are only sometimes visible at low tide.
This tune is Irish in style but may have originated in the US before its spread through much of the traditional music world. It is also known as a hornpipe named Katherine Brennan's Favorite, which came from Irish-American fiddler Andy McGann, who learned it from his fiddle teacher Katherine Brennan.