'areometry' originates from New Latin/French (via 'areometer'/'aréomètre'), ultimately from Greek 'αραίος' ('araios') meaning 'thin, rare' plus Greek 'μέτρον' ('metron') meaning 'measure'.

'areometry' developed from French 'aréomètre' and New Latin 'areometria' and was adopted into English as 'areometry' to denote the measurement of rarity/thinness (i.e., specific gravity) of liquids.

Initially it related to the idea of measuring 'rarity' or 'thinness'; over time this specialized to the modern technical sense of measuring density or specific gravity of liquids.