I agree with @Original ji. He has proved my point in a much better manner than I did. I thank him for that.Sir, the word "rom" is commonly used as an adjective [Punjabi, language n literature], meaning, "permeating every fibre of the body/or space". Take for example, the shabd [ਚਉਦਸਿ ਚਉਦਹ ਲੋਕ ਮਝਾਰਿ ॥ ਰੋਮ ਰੋਮ ਮਹਿ ਬਸਹਿ ਮੁਰਾਰਿ ॥ ਸਤ ਸੰਤੋਖ ਕਾ ਧਰਹੁ ਧਿਆਨ ॥ ਕਥਨੀ ਕਥੀਐ ਬ੍ਰਹਮ ਗਿਆਨ ॥੧੫॥ 344,SGGSJ]. Translation [bold]...god occupies/lives in every fibre [rom rom]. Note - the word rom is always used consecutively, that is, one after the other [rom rom], to strengthen meaning and context.
Yes, Rom means "permeating every fibre of the body/or space".
However, in this expression, fibre does not mean hair.
i love you with every fiber in my body
It means this girl/boy really truly loves you with every thing in them down to the last atom and molecule. Most people who say it are truly in love.
"I love you with every fiber in my body"
Urban Dictionary: i love you with every fiber in my body
Hence, it is the perfect expression used but it has nothing to do with hair as wrongly translated in the SGGS by the Christian missionaries who had fallen in love with Sikhi.