The phrase “swaddling clothes” is a translation of the root Greek word Sparganoo. The word appears in 2 verses in the New Testament in Luke 2. The 1st appearance of Sparganoo occurs in verse 7 & the 2nd is in verse 12.
The Greek word Sparganoo means “to wrap a child in swaddling clothes (long strips of cloth)” or “to clothe in strips of cloth, to wrap up in strips of cloth, to wrap in cloths.” Swaddling is an old practice of wrapping infants in blankets or cloth to restrict the movement of arms & legs.
Record of swaddling is in the New Testament description of the birth of Jesus in Luke 2:6–2:7: "And so it was, that, while they were there, the days were accomplished that she should be delivered. And she brought forth her firstborn son, and wrapped him in swaddling clothes and laid him in a manger."
When the angel appeared to the shepherds in the field, he declared Christ‘s birth to them and he gave them a sign. And what was that sign? Luke 2:9-12 reads "And, lo, the angel of the Lord came upon them, and the glory of the Lord shone round about them: and they were sore afraid. And the angel said unto them, Fear not: for, behold, I bring you good tidings of great joy, which shall be to all people. For unto you is born this day in the city of David a Saviour, which is Christ the Lord.And this shall be a sign unto you; Ye shall find the babe wrapped in swaddling clothes, lying in a manger."