'agate-set' originates from English, specifically the compound of the noun 'agate' and the verb/noun 'set', where 'agate' meant a very small size of type and 'set' meant 'to arrange or compose'.

'agate' itself comes into English via French 'agate' and Italian 'agata' ultimately from Latin 'achates' and Greek 'Achates' (the name of a river and the semiprecious stone). The typographic sense ('a small type size') developed later in English printing usage; combining it with 'set' produced 'agate-set' for text arranged in that size.

Initially 'agate' referred to the semiprecious stone; over time the word was applied to a very small size of type and then to text composed in that size, yielding the meaning of 'agate-set' as text arranged in very small type.