Etymology Map
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Litmus

3 stages from Old Norse to English.

Today it means a dye from lichens that turns red in acid and blue in alkali

Where does the word "litmus" come from? It comes from Old Norse litmosi, passing through Middle Dutch before entering English (1500s).

1
Stage 1 of 3
litmosi
Old Norse · medieval
"dye moss"
'dye-moss', from 'litr', colour, and 'mosi', moss: lichens used for dyeing
2
Stage 2 of 3
lakmoes
Middle Dutch · 1400s
"lichen dye"
Dutch dyers processed the lichen into a blue dye
3
Stage 3 of 3
litmus
English · 1500s
"acid-base indicator"
chemists used litmus paper to test acids; 'litmus test' as a decisive test dates from the 1950s
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Read the full story

Litmus’s story begins in Old Norse: litmosi meant “dye moss.” 'dye-moss', from 'litr', colour, and 'mosi', moss: lichens used for dyeing. By 1400s, the word had taken hold in Middle Dutch as lakmoes. Dutch dyers processed the lichen into a blue dye. It reached English by 1500s as litmus. Chemists used litmus paper to test acids; 'litmus test' as a decisive test dates from the 1950s. Today, litmus means a dye from lichens that turns red in acid and blue in alkali.