Lesbia Weeping over a Sparrow by Sir Lawrence Alma-Tadema, 1866
Depression. Which is what I would be in right now after the failure of my primary coffee pot if I did not have a French press to serve as backup . . . 😉
Naw, seriously, this is another word I had to look up for my work-in-progress. See, I’ve learned to be careful about any word or phrase that is used in modern psychology, because many of them are either plain ol’ new or with new meaning since Freud and company came along, but so much in today’s common vernacular that we often don’t even pause to consider them… So I thought depression had better be investigated.
Apparently the first appearance of the word was in the 14th century, as a term in astronomy.  I admit I had to look this one up, because I couldn’t fathom, on this Monday morning with belated coffee, why in the universe astronomy would employ this word. Until I saw the phrase “the sun at an angle of depression…” Ah. Angles. Right. Moving on.
Pretty much all connotations of depression stem from the literal “pressing down” of something, though that above sense pre-dates the literal meaning by 300 years. Go figure! For that matter, even the most familiar “dejection” is from the 15th century, so pre-dates the literal.
Of course, do keep in mind that when older texts (or historical fiction, LOL) refer to someone experiencing depression, this is merely a description of low spirits, not a clinical term. The clinical term didn’t come about until 1905.
But we also have a few more meanings that come from those in-between years. In 1826, depression was applied to “a reduction in economic activity.” And then in 1881 the meteorological meaning joined the team in reference to barometric pressure. Talk about a word with meanings in every sphere! The celestial one, the atmospheric one, through our wallets and all the way to our spirits. 
Interesting indeed!
Hope everyone has a lovely October week full of no depression other than the atmospheric and celestial types. 😉