My current research theory is that the term "skeleton suit" comes from the 1820's.
Thes are the inspirational images I am looking at as I draft my pattern.
The Sackville Children, by John Hoppner, 1796. Jacket and trousers are different colors. slightly raised waist. The boy is about 3 or 4 years old.
Frederick Seymour and Sir Horace Seymour K.C.H., by Henry Edridge, sold at Christies in 2010
The Hülsenbeck children, by Philipp Otto Runge1805-10. Green with short sleeves, high waist
Sketch version is dated 1805-6
The Woolsey Family, by William Berczy, 1809 both boys in green, natural waist
Also take a look at WikiCommons for more
Museum of London has an example that is earlier than what I am looking at.
Tidens Toj late 18th century
Tidens Toj 1800
suit sold at Christies in 1999
Metropolitan Museum 1983.3.1a, b red and white strip cotton c.1820