The Shape of Sleep

I was doing a crossword puzzle and one of the words in it was "chloroform", which got me thinking: "chlor-" is obviously from the element "chlorine", but "-form" means "shape", and how on Earth did that into the word?

How easily we're led astray by our own ignorance! If I'd ever had any training in chemistry, I might have known that the "-form" in "chloroform" is an abbreviation of "formyl", which has something--I am really not entirely sure what, but it's certainly chemistry--to do with formic acid. (A little bit more about formic acid, plus a bunch of other ramblings, here.) A chloroform molecule is composed of three chlorine atoms plus, I guess, a formyl group, which, and this is the part I don't quite get, has the chemical formula HCO, but chloroform's formula is CHCl³, and where did that oxygen molecule go?

"Formyl" looks kind of like "formula", doesn't it? If you know that the emperor Caligula's childhood nickname means "little boots", you might guess, and correctly, that "-ula" is here a Latin diminutive, as in "uvula", "little grape". (This "-ula" is not to be confused with the "-ula" that naturally occurs as a plural of words ending in "-ulum", as in "speculum/specula" and "reticulum/reticula", or with words that simply happen to end in "-ula" such as "macula" and "nebula".) "Formula" is indeed originally a little form--a single method for doing something, specifically the words to a religious ceremony.