A mix of Hurricane Ophelia and Saharan dust storms turned the sun an ominous red over much of the UK earlier this week. It also caused the sky to look an eerie yellow or, as many commented, sepia. And this fancy color word, as it turns out, has a very cuttle-y, and very un-cuddly, origin.

Sepia’s undertones

Sepia is in a special class of etymologies we’ve seen a few times before on the blog: everyday words derived from inks or dyes obtained from the secretions of bugs or mollusks. Purple was originally the “purple-colored dye” produced by sea snails. Shellac goes back to the “dark red dye” made from certain insects. And sepia ultimately means “cuttlefish” in Ancient Greek.

Yes, you’re favorite Instagram filter has it roots in a squid-like mollusk. (The cuttle in cuttlefish, while we’re at it, is from the Old English cudele, possibly from a Germanic root meaning “bag,” referring to its ink sac).

Sepia is first found in English in 1569, the Oxford English Dictionary tells us, as another name for the “cuttlefish,” from the Latin via Greek sepia (σηπία). When the cuttlefish is alarmed, it can emit a special ink, from which we’ve been making a rich, brown pigment since antiquity.

Sepia pigment was popular in monochrome watercolor paintings in the 19th century, and so we see sepia referring to it by 1821, here borrowed from the Italian seppia. Sepia tones were also popular in monochrome photography in the late 19th and early 20th centuries, hence our associations with the color.

As for the deeper origins of the Greek sepia, etymologists connect it to the verb sepein, (σήπειν), “to rot.” The thinking goes, the cuttlefish “befouls” the water when it spits its dark ink.

The noun form of sepein was sepsis (“putrefaction,” σῆψις), which has been used since the late 19th century in medicine for a kind of widespread infection in the body. A septic tank, as certain bacteria break down our waste, features the adjective form of the word, and antiseptic, or “sterilized to the point of dullness,” shows the further life of the word. The prefix sapro– is also related, meaning “rotten,” e.g, saprogenic, “causing decay.”

England’s sepia sky, we might say, looked a bit sickly, jaundiced—or septic, if we’re to apply today’s etymological insights.