In 1811 (according to Wikipedia), the German chemist Johann Schweigger proposed that the element which Humphry Davy had named 'chlorine' be renamed 'halogen'. Schweigger coined this word by combining the Greek words for 'salt' and 'to beget': αλς [als] and γενιεν [genein].
Davy's name prevailed, but in 1826, the Swedish chemist Baron Jöns Jacob Berzelius proposed that Schweigger's name be used for for the elements fluorine, chlorine and iodine collectively, as they all produce a sea–salt–like substance when they form a compound with an alkaline metal.
What Wikipedia doesn't tell us is how Schweigger got from 'als' to 'halo'.
© Haydn Thompson 2020