What does anthem mean?
The definition of anthem
An”them, n.
Etym: [OE. antym, antefne, AS. antefen, fr. LL. antiphona, fr. Gr. anthaine, anteine, antieune, F. antienne. See Antiphon.]

1 Formerly, a hymn sung in alternate parts, in present usage, a selection from the Psalms, or other parts of the Scriptures or the liturgy, set to sacred music.
2 A song or hymn of praise. Milton.

An”them, v. t.
To celebrate with anthems. [Poet.] Sweet birds antheming the morn. Keats.