'coatable' is formed in English from the noun/verb 'coat' and the suffix '-able'. 'coat' originates from Old French 'cote' (from Late Latin 'cotta'), meaning 'a garment' or 'outer covering', and the suffix '-able' ultimately comes from Latin '-abilis' via Old French, meaning 'capable of'.

'coat' changed from Old French 'cote' (a tunic or garment) and entered Middle English as 'cot'/'cote', later becoming the modern English 'coat'. The adjectival suffix '-able' was borrowed into Middle English from Old French '-able', itself from Latin '-abilis', and combined with English verbs and nouns to form adjectives like 'coatable'.

Originally 'coat' primarily referred to a garment; over time it developed a verbal sense 'to cover with a layer' (e.g., to coat with paint). Consequently, 'coatable' came to mean 'able to be covered or given a coating' in the material/technical sense.