hemistich (n.)

"half a poetic line," 1570s, from Middle French hémistiche (16c.) or directly from Late Latin hemistichium, from Greek hēmistikhion "half-line, half-verse," from hēmi- "half" (see hemi-) + stikhos "row, line of verse," from PIE *stigho-, suffixed form of root *steigh- "to stride, step, rise" (see stair). Related: Hemistichal.