Octave has been derived from the Latin word octāva, which means “eighth part.” It is a verse form that contains eight lines, which usually appear in an iambic pentameter.
[1][2] An octave is a verse form consisting of eight lines of iambic pentameter (in English) or of hendecasyllables (in Italian).
In Milton's Sonnet 19, the sestet begins early, halfway through the last line of the octave: When I consider how my light is spent Ere half my days in this dark world and wide, And that one talent which is death to hide Lodg'd with me useless, though my soul more bent
To serve therewith my Maker and present My true account, lest he returning chide, "Doth God exact day-labor, light denied?"
That murmur, soon replies: "God doth not need Either man's work or his own gifts: who best Bear his mild yoke, they serve him best.