SAD, a. It is probable this word is from the root of set. I have not found the word is from the root of set. I have not found the word in the English sense, in any other language.

1. Sorrowful; affected with grief; cast down with affliction.

Th' angelic guards ascended, mute and sad.

Sad for their loss, but joyful of our life.

2. Habitually melancholy; gloomy; not gay or cheerful.

See in her cell sad Eloisa spread.

3. Downcast; gloomy; having the external appearance of sorrow; as a sad countenance. Matt. 6.

4. Serious; grave; not gay, light or volatile.

Lady Catherine, a sad and religious woman.

5. Afflictive; calamitous; causing sorrow; as a sad accident; a sad misfortune.

6. Dark colored.

Woad or wade is used by the dyers to lay the foundation of all sad colors.

This sense is, I believe, entirely obsolete.

7. Bad; vexatious; as a sad husband. Colloquial.

8. Heavy; weighty; ponderous.

With that his hand more sad than lump of lead. Obs.

9. Close; firm; cohesive; opposed to light or friable.

Chalky lands are naturally cold and sad. Obs.

The two latter senses indicate that the primary sense is set, fixed.