lit adj.

"blue dye-stuff obtained from certain lichens," early 14c., lit-mose, probably from an Old Norse word related to Norwegian dialectal litmose, from Old Norse lita "to dye, to stain" (from litr "color, dye;" see lit (n.1)) + mos "moss." Said to be also in part from Middle Dutch lijkmoes (Dutch lakmoes), from lac (see lac) + moes "pulp." Another idea [Watkins] connects the first element to Middle Dutch leken "to drip, leak" (see leak (v.)). The second element is in any case the common Germanic word for "moss, lichen" (see moss).

The dye is obtained from certain lichens. It is naturally blue but turns red in acid and is restored to blue by alkalis. Figurative use of litmus test is first attested 1957, from scientific use of litmus-treated paper as a chemical indicator. Litmus paper with this meaning is from 1803.

early 15c., "book-learning," from Latin literatura/litteratura "learning, a writing, grammar," originally "writing formed with letters," from litera/littera "alphabetic letter" also "an epistle, writing, document; literature, great books; science, learning" (see letter (n.1)). In English originally "book learning" (in which sense it replaced Old English boccræft); the meaning "activity of a writer, the profession of a literary writer" is first attested 1779 in Johnson's "Lives of the English Poets;" that of "literary productions as a whole, body of writings from a period or people" is first recorded 1812.

Great literature is simply language charged with meaning to the utmost possible degree. [Ezra Pound, "ABC of Reading"]

Meaning "the whole of the writing on a particular subject" is by 1860; sense of "printed matter generally" is from 1895. The Latin word also is the source of Spanish literatura, Italian letteratura, German Literatur.