1841, also sextette, "work for six voices," altered (by influence of German Sextett) from sestet (q.v.). As "company or group of six persons or things" by 1873.
Entries linking to sextet
sestet n.
1801, in music, from Italian sestetto, diminutive of sesto "sixth," from Latin sextus (see Sextus). Same as sextet. More usually "the concluding two stanzas (six lines) of a sonnet" (1859).