If one is a civil Poet, and one is aware (in this case, through other persons' learning on which one has piggybacked) that a phrase was created, say, by Apollonius Rhodius, the polite and refined gesture would be to include an acknowledgement of the Poet and his poem which provided the phrase. Just to apprpriate it without citation seems, to me, to be a clodhopping hayseed's snatch-n-grab.