Appears at first glance to be from Middle English leyer, leyare (“a layer of stones or bricks”), equivalent to lay + -er. In which case, ultimately identical to etymology 2 below. For the pronunciation compare prayer. However, this word layer (referring to a thickness of a material covering a surface) has also been argued to be from a respelling of an obsolete sense of the word lair that was once used by farmers, which had to do with soil. The connecting sense between the usual meaning of lair and the specialised farming meaning was: an area where cows typically rest, the ground being fertilised by their waste. Related to lie, ledger.
A single thickness of some material covering a surface.
Wrap the loaf in two layers of aluminum foil before putting it in the oven.
After the first coat of paint dried, he applied another layer.
2
An item of clothing worn under or over another.
It's cold now but it will warm up this afternoon. Make sure you wear layers.
3
A (usually) horizontal deposit; a stratum.
I find seven-layer cake a bit too rich.
Sometimes, the underlying layers are exposed by erosion, revealing the story of the rocks like an open book.2012, Chinle Miller, In Mesozoic Lands: The Mesozoic Geology of Arches and Canyonlands National Parks, Kindle edition:
4
One of the items in a hierarchy.
mired in layers of deceit
Right above the database access layer sits a number cruncher that performs any calculations that a particular request may require, such as computing a standard deviation. In many cases, this layer just forwards raw numbers.2001, C/C++ Users Journal, volume 19, page 38:
5
Computer graphics, Computing, Engineering, Mathematics, Natural sciences, Physical sciences, Sciences One in a stack of (initially transparent) drawing surfaces that comprise an image; used to keep elements of an image separate so that they can be modified independently from one another.
By analogy to a stack of transparencies
6
Computing, Engineering, Mathematics, Natural sciences, Networking, Physical sciences, Sciences One of the seven network switch pieces in the Open Systems Interconnection model: application, presentation, session, transport, network, data link, and physical.
7
Computing, Engineering, Mathematics, Natural sciences, Physical sciences, Sciences An alternative keymap accessed through a modifier key or toggle.
Appears at first glance to be from Middle English leyer, leyare (“a layer of stones or bricks”), equivalent to lay + -er. In which case, ultimately identical to etymology 2 below. For the pronunciation compare prayer. However, this word layer (referring to a thickness of a material covering a surface) has also been argued to be from a respelling of an obsolete sense of the word lair that was once used by farmers, which had to do with soil. The connecting sense between the usual meaning of lair and the specialised farming meaning was: an area where cows typically rest, the ground being fertilised by their waste. Related to lie, ledger.
1
Ambitransitive To cut or divide into layers.
2
Ambitransitive To arrange in layers.
Layer the ribbons on top of one another to make an attractive pattern.
layer
noun
US /ˈleɪ.ɚ/
Etymology From lay + -er.
1
A person who lays anything, such as tiles or a wager.
If fortune ever favoured any venturesome layer of bets, Tom Elliot was certainly the one that day.1890, The Argosy, volume 49, page 183:
2
A mature female bird, insect, etc. that is able to lay eggs.
As for which hen we'll cull for next Sunday's dinner, we certainly won't eat Henrietta yet — she's still a prime layer.
When dealing with an infestation of headlice, the first step is to eliminate the layers.
3
A hen kept to lay eggs; a breed of chicken bred to maximize laying output.
“Mrs. Boast can’t have got all these from one hatching,” [Ma] said. “I do believe there’s not more than two cockerels among them.” “The Boasts have got such a head-start with chickens, likely they’re planning to eat friers this summer,” said Pa. “It may be she took a few cockerels out of this flock, looking on them as meat.” “Yes, and replaced them with pullets that will be layers,” Ma guessed. “It would be Mrs. Boast all over. A more generous woman never lived.”1941, Laura Ingalls Wilder, Little Town on the Prairie: