It's a lovely vroom of a word - like a car in wet weather - but, perhaps sadly, it's actually a clothes thing.
A ruche can be a strip of gathered or pleated fabric used as a decoration on an item of clothing, or, if you're still living in the eighteenth century (and there are those) then it's a sort of mini ruff worn round the neck.
Landgravine Victoria of Hesse-Rotenburg
Ruching is when you sew lines of parellel stitches, possibly, but not necessarily, using the very thin elastic called shirring elastic, so you end up with an area of gathered fabric:
ruched dress by Jean-Paul Gaultier
Sadly, at the moment you probably have to be female to wear ruching, though actually...
...perhaps Messrs Barnier and Davis should set an example of flexibility and show us some ruching at the next round of Brexit talks.
...though actually perhaps not.
Word To Use Today: ruche. This word came from France, where it means beehive, in the 1800s. I do not understand this at all. Before that it came from the Latin rūsca, the bark of a tree, from some Celtic language.