Zetlandic typically occurs fewer than 0.01 times per million words in modern written English.
Zetlandic is in frequency band 1, which contains words occurring fewer than 0.001 times per million words in modern written English. More about OED's frequency bands
Frequency data is computed programmatically, and should be regarded as an estimate.
Frequency of Zetlandic, adj., 1800–2010
* Occurrences per million words in written English
Historical frequency series are derived from Google Books Ngrams (version 2), a data set based on the Google Books corpus of several million books printed in English between 1500 and 2010.
The overall frequency for a given word is calculated by summing frequencies for the main form of the word, any plural or inflected forms, and any major spelling variations.
For sets of homographs (distinct entries that share the same word-form, e.g. mole, n.¹, mole, n.², mole, n.³, etc.), we have estimated the frequency of each homograph entry as a fraction of the total Ngrams frequency for the word-form. This may result in inaccuracies.
Smoothing has been applied to series for lower-frequency words, using a moving-average algorithm. This reduces short-term fluctuations, which may be produced by variability in the content of the Google Books corpus.
Decade
Frequency per million words
1800
0.0022
1810
0.0018
1820
0.0015
1830
0.0017
1840
0.0017
1850
0.002
1860
0.0017
1870
0.0018
1880
0.0018
1890
0.0018
1900
0.0014
1910
0.0006
1920
0.0002
1930
0.0002
1940
0.00008
1950
0.00006
1960
0.00006
1970
0.00006
1980
0.00002
1990
0.00003
2000
0.00004
2010
0.000007
Originally published as part of the entry for Zetland, n.