SAD, adjective [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. Matthew 6:16.
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. obsolete
9. Close; firm; cohesive; opposed to light or friable.
Chalky lands are naturally cold and sad obsolete
[The two latter senses indicate that the primary sense is set, fixed.]