Cleavers or Goosegrass

Many a country walk with children involves sticking cleavers or goose grass on people's backs, ideally without them realising. It's a common plant and one of the first out of the gates in spring. It's also difficult to get rid of once it gets a roothold in your garden, even though it's an annual.
It's actually edible and has been used for all sorts of things, from stuffing mattresses and making sieves, to dying cloth red (the root) and providing a coffee substitute (roasted seeds).
It's binomial is Galium aparine and it's in the fourth biggest family of flowering plants, Rubiaceae. Coffee and bedstraws are siblings. The family belongs to the order is Gentianales after the gentians, which themselves are named for the Illyrian king Gentius. I hope that's clear.