Honorific term for an older or respected person. Rare in modern Japanese; more common in classical or formal contexts.
The village elders gathered and discussed.
wife's father; father-in-law
Specifically refers to one's wife's father. Also rare; 義父 (ぎふ) or お義父さん are more common in modern speech.
He deeply respects his father-in-law.
From Chinese 丈人 (zhàngrén), originally meaning 'elder' or 'man of stature'. The specific meaning 'wife's father' developed later. The exact historical derivation in Japanese is uncertain.