A loose outer garment; especially, a gown forming a part of European modern costume for women and children; also, a coarse shirtlike garment worn by some workmen over their other clothes; a smock frock; as, a marketman's frock
A frock coat was a long coat that was worn by men in the 19th century. A man's dress coat or suit coat with knee-length skirts. a knee-length coat for men, worn in the 19th century
[ 'fräk ] (noun.) 14th century. From Old French froc, from Frankish *hroc. Compare German Rock (“coat”) and late Old Norse rokkr ( > Danish rok (“garment”), archaic, if not in compounds).