Couplet (noun)

1. A pair of successive lines of verse, especially rhyming lines, in a poem or song.
2. A pair of things that are similar or complementary.

Origin:

Late middle english: from old french couplet, from latin cōpula "tie", from cōpulāre "to join together".

Examples:

1. The couplet in the song was repeated several times.
2. She recited a couplet from the poem.
3. The couplet of birds perched on the branch.
4. The couplet of paintings hung on the wall.
5. The couplet of shoes in his closet were both made of leather.