St. Patrick, the shamrock, and the Trinity

St. Patrick used a shamrock to explain the Trinity right? Ummmmmmm ….

http://christianity.stackexchange.com/questions/17724/did-saint-patrick-actually-explain-the-trinity-using-a-shamrock

TL;DR: There is no written mention of this until the 18th Century, and it’s a bad metaphor anyhow.