Arcades ambo [ˈɑːkədiːz ˈæmbəʊ] n.
1.) Two persons of the same tastes, profession, or character (often derogatory) (O.E.D. 2nd Ed.).
Etymology: Latin, 'both Arcadians', i.e. both pastoral poets or musicians. The phrase originates in Virgil's Eclogues.
"Forte sub arguta consederat ilice Daphnis,
compulerantque greges Corydon et Thyrsis in unum,
Thyrsis ouis, Corydon distentas lacte capellas,
ambo florentes aetatibus, Arcades ambo,
et cantare pares et repondere parati" (Eclogues, Publius Vergilius Maro, ~38 B.C.).
"Daphnis beneath a whispering holm reclined,
And near him Corydon and Thyrsis join'd
Their flocks; his sheep one pastured on the lawn,
And one his goats with udders yet undrawn:
Both freshly blooming, both of Arcady,
Skill'd or to lead the lay, or to reply (Virgil, John Dryden, William Sotheby, and Francis Wrangham (trans.), 1830).