amber vs umber

amber

adj
  • Of a brownish yellow colour, like that of most amber. 

noun
  • A hard, generally yellow to brown translucent fossil resin, used for jewellery. One variety, blue amber, appears blue rather than yellow under direct sunlight. 

  • The stop codon (nucleotide triplet) "UAG", or a mutant which has this stop codon at a premature place in its DNA sequence. 

  • Hesitance to proceed, or limited approval to proceed; an amber light. 

  • A yellow-orange colour. 

  • The intermediate light in a set of three traffic lights, which when illuminated indicates that drivers should stop short of the intersection when safe to do so. 

verb
  • To take on the yellow colour of amber. 

  • To cause to take on the yellow colour of amber. 

  • To perfume or flavour with ambergris. 

  • To preserve in amber. 

umber

adj
  • Of a reddish brown colour, like that of the pigment. 

noun
  • A dusky brown African wading bird (Scopus umbretta) allied to the shoebill and herons; a hamerkop. 

  • A grayling. 

  • A brown clay, somewhat darker than ochre, which contains iron and manganese oxides. 

verb
  • To give a reddish-brown colour to. 

How often have the words amber and umber occurred in a corpus of books? (source: Google Ngram Viewer )