The English word ruche [ɹuʃ] means a gathered ruffle or pleat of fabric used for trimming or decorating garments [source], or to flute, pleat or bunch up (fabric) [source].

It comes from the French word ruche [ʁyʃ], which means a (bee)hive, ruffle or flounce, and comes from the Middle French rusche (beehive), from the Medieval Latin rusca (bark), from the Gaulish *ruskā, from the Proto-Celtic *rūskos (bark, beehive) [source], from the Proto-Indo-European h₃rewk- (to dig (up), till) [source].

Words from the same Proto-Celtic root include:

• rusk [rysk/ʁysk] = bark, zest, beehive, bread pan;
  ruskenn = (bee)hive, apiary, frill, ruche (Breton)
• rusc [rusk] = (bee)hive (Catalan)
• rusk [ɾyːsk] = bark, peel (Cornish)
• Reuse [ˈʁɔʏ̯zə] = fish trap, cage, shrimping net (German)
• rúsc [ɾˠuːsˠk] = bark (of a tree); vessel made of bark (Irish)
• roost [ruːst] = peel, bark, rind (Manx)
• ruse [ˈrʉːsə] = fish trap (Norwegian)
• rùsg [r̪ˠuːsɡ] = (tree) bark, peel, rind, husk, crust, fleece (Scottish Gaelic)
• ryssja [rʏɧːa] = fish trap (Swedish)
• rhisgl [ˈr̥ɪsɡl/ˈr̥ɪsɡɪl] = bark, rind, peel, husk (Welsh)

Sources: Grand Terrier Edition Skol Vreizh, TERMOFIS, catalandictionary.org, gerlyver kernewek, ReversoDictionary, teanglann.ie, On-Line Manx Dictionary, Bokmålsordboka | Nynorskordboka, Am Faclair Beag, Svenska Akademiens Ordböcker, Geiriadur Prifysgol Cymru