Origins of Nomenclature

From 'pent-' onwards, the names make sense (they are just Greek numbers); but the first four were all formed by truncating the names of chemical compounds

methyl

'methyl' comes from methyl alcohol (what we now call methanol).
"Methyl alcohol" is from the Greek words for 'wine' (mequ, methu) and 'wood' (ule, ule) since it was a spirit that had been distilled from wood

ethyl

'ethyl' comes from ether (what we now call diethyl ether)
"Ether" was named because its transparency and light weight reminded its discoverers of air (Latin 'æther')

propyl

'propyl' comes from propionic acid (propanoic acid)
"Propionic acid" was named from the Greek words for 'first' (pro, pro) and 'fat' (pion, pion) - so-called because it was the first of the true fatty acids, after the highly polar formic and acetic acids

butyl

'butyl' comes from butyric acid (butanoic acid)
"Butyric acid" was named since it was discovered in butter (Latin 'butyrum')