life; breath of life
Archaic poetic term for life or the thread of life, literally 'cord of breath'. Found in classical Japanese literature; not used in modern everyday speech.
息の緒 was used in old waka poetry as a word expressing the thread of life.
Compound of 息 (breath) and 緒 (cord, thread). The image is of breath as a thread that sustains life; the exact historical derivation is uncertain.