Other forms: frills
A frill is a strip of cloth gathered along one edge and sewn on so that it ripples. The wavy trim round the bottom of a curtain, the ruffle down the front of an old dress shirt, the loose edge on a lampshade.
In the plural it stops being cloth and means the extras you could live without, which is what a no-frills airline sells you: a seat, and nothing around it. Animals have frills of their own, from the bone shield fanning out behind a Triceratops skull to the flap of skin a frilled lizard snaps open to look twice its size. The adjective frilly belongs to clothes and curtains and carries a hint of too much, as in a frilly pink cake or a frilly blouse. Frill and ruffle name so nearly the same thing that sewing patterns use them almost interchangeably.
1nounfrillA gathered or pleated strip of cloth sewn on as decoration.
“She sewed a frill along the hem of the curtain.”
2nounextrasFrills: extras that are pleasant but not needed.
“The hotel is clean and cheap, with no frills at all.”
3nounfanA fan of bone or skin around an animal's neck.
“The frill behind a Triceratops skull could be a metre across.”
frill is a decorative strip of cloth.
Frill comes from Old French friller. That is the whole recorded chain: one word, one language, and then English cloth. For a word about decoration it has a remarkably plain history.
Old French
friller
English, today
frill
From Old French friller.
Etymology from Wiktionary, CC BY-SA
Practised in Clothes & Fashion, Dinosaurs & Prehistory, Knitting & Sewing