A canopy or assembly sign 亼 above 卩, a person kneeling — someone on their knees beneath authority, receiving instructions. The character has meant command since the oracle bones, and it still names the officials who gave them: a county magistrate was a 县令.
命令 is an order, 法令 a decree, 口令 a password. 令 also softens into 'to cause': 令人满意 means satisfying, literally 'causes people to be satisfied'. In polite old-fashioned speech 令 honours the listener's family — 令尊 is your father, respectfully.
Someone KNEELING under a canopy of authority, taking the ORDER.
令人 plus an adjective is one of the most productive patterns in Chinese: 令人感动 (moving), 令人失望 (disappointing) — literally 'causes people to be…'.